What are some general mixing tips? Ofc i know every rip is different and stuff is suggestive but i mean like when and how would i use eq, when and how would i use reverb, when and how would i use delay, when and how would i use compression
You have a good point in that every rip (or song or whatever you're doing) is different, even if it's derivative you're making a piece of art so there's plenty of ways to approach it. There's definitely ways to mix that most people would consider sounding better than others, but getting that right is tricky if you can't reliably hear the difference. For a while I didn't really have an ear for these things (hearing clashing and/or subpar mixing) so I just had to go off what other people told me. Eventually, to my surprise, I started to develop an ear for this and now I can judge both my own rips and other people's rips on various criteria. I think that's probably just from raw practice. (Note: I don't have perfect pitch but you don't need that, I have a decent sense of relative pitch now and often use Melodyne to more accurately measure what I'm hearing.) Here's a handful of examples of when I use all of the things you mentioned. This is really not comprehensive, it's just a lot of different tips I remembered.
EQ
Note: You might want to keep the names of frequency ranges in mind here for what I'm saying. If you open Fruity parametric EQ 2 in FL, you can see at the top that it's divided into SUB, BASS, LOW MID, MID, HIGH MID, PRS, and TREBLE. You can find this out by testing, but generally:
bass instruments will be in SUB and BASS (of course). But that's not the only thing that will be there, "bass" is not only an instrument name but a range of frequencies.
Vocals will be roughly around the MIDs, usually.
hi-hats, cymbals and other "wispy" sounding things (like sibilants, the "sh", "t", "ch" in vocals etc) will tend to be in the highest range, near TREBLE or whatever PRS is meant to mean.
Everything else varies wildly, but the good thing is that with visual EQ you can test and hear for yourself what sounds are spread across what frequencies, by reducing or raising them.
Golden rule of EQing mashups: In general, you want to strike a balance in the frequencies between the sources. If one source is naturally strong in the high mids (like in its vocals), you may want to reduce the high mids of the other source to compensate. These songs were not originally designed to be together, so the goal is to somehow make them feel like a cohesive whole. This is why using split stems/multitracks really helps, because you can more accurately reduce certain instrumental elements than a soft EQ would have (for example, by totally removing the bassline of one of the sources so that it doesn't sound muddy against the other source's bass.) Like everything here though, how much you should follow this "rule" would vary in practice depending on the music.
Specific EQ tips:
On DIY vocals I always remove the sub and some of the bass (not too much to where it heavily affects how they sound) because those don't need to be there. I think it cleans up the mix a little bit.
If vocals sound too harsh or piercing, I often lower the high mids. Melodyne pitch-shifting and stretching on certain vocals can sometimes cause that.
Similarly, if percussion is too harsh-sounding, I may lower the highs (treble) a bit, but carefully and not too much.
Reverb
This is another one where… I just use it when it sounds nice. I like putting a little bit of reverb on vocals when it feels like the mix needs it, and sometimes I do it when it probably doesn't need it. Taking FL Studio's Reeverb as an example, the knobs you may want to fiddle with the most would be SIZE, DEC (decay), DRY/WET, H.CUT/L.CUT and maybe BASS?
If I used a de-reverb algorithm on vocals so that I could pitch-shift them better, I would always put a reverb effect back on when I add the vocals into the mix.
One useful thing to note: when you add reverb (particularly to vocals) it's probably a good idea to increase the low cut, this can make the reverb sound less muddier and generally better. This is a tip I gathered from a friend, and posted to Twitter last year.
(There's also stuff to say about convolvers and impulse responses in regards to matching reverb in sequenced music, but I feel like that's outside the scope of this post.)
Delay
Delay makes echo(es) repeated across intervals. You can make the delay panned if you want (even back-and-forth between the ears), or you can make its frequency cutoff reduce with further echoes (sort of a "going underwater" effect), among other options. One thing I use delay for in mashups is when I'm covering a lead melody with vocals and the lead in the instrumental has a delay channel or effect, so I find it fun to match that effect on the vocals too, with the same delay time and panning.
Sometimes you might just want to do it for fun, or to make something sound less empty. In Circus (HQ Audio) - Five Nights at Freddy's I added delay to the vocals. The original Right Foot Creep vocals don't really have any; the Most Mysterious Song vocals might have a little but that didn't matter to me. I added them because it sounded cool and more "full" (one reason might have been the short syllables with more empty space between lines than Right Foot Creep's lyrics normally provide.)
Compression
This one is actually an area I'm less familiar with. I certainly didn't understand compressors for a while, and I usually prefer to use the limiter because the visual aid really helps me understand what's happening to the sound. (That's really just me though, plenty of people I know use other things like Fruity Compressor or common third-party VSTs like OTT, look into these if you're interested.) But they're a very important tool for mixing, and I can definitely think of reasons I would use compressors or limiters:
Evening out the level of vocals. It helps the sound of vocals to have most words be roughly around the same volumes. DIY vocals can especially have this issue, for various reasons relating to how the instrumental may have affected them. A limiter that just smoothes off the high peaks of vocals can be a simple way to solve that. If you want to do it more "finely" for a possible better sound, there's lots of ways syllable volumes can be changed individually. That includes volume automation, clips in the newer versions of FL, Melodyne's amplitude tool, etc.
Compressing drums to make them sound tighter. Again, something that's hard for me to describe at my current level of knowledge/skill lol. I would suggest to put the "Drums" preset in Fruity Compressor on a drum stem and hear what happens to it, as one example of how you can change the texture of a sound through compression.
I can use this topic to talk about the master limiter too. Generally when I'm mixing a rip I like having the volume sort of generally approach the limiter ceiling, maybe going over it a little bit on occasion but not too much of the time. If you compress/limit something too hard, it can become a "brick wall" and will certainly sound like it. (Again, sometimes that could be what you're going for!)
Final note - don't be afraid to use automation clips to change any of these effects' values throughout the track. It's possible that you may want to EQ certain words or lines harsher than others, for example, or that it's appropriate for one section of a melody to have more reverb than the other. Once you get a good feel for what sounds better, you might start going crazy with automation like I have on occasion, but that's not usually expected.
I wrote a lot, but there's definitely parts of this that are lacking in detail either because I thought it was too much for this post, don't have enough knowledge or just couldn't explain it well. If you have any further questions please feel free to ask.
