skill and playtest for the player questions and homebrew for the dm questions
Playtest: What class (or subclass) do you want to try out?
This is going to sound like the most 5E DM thing ever, but honestly? Battle Master Fighter. However, I think because of how Fighter is in terms of utility, the likelihood of me ever playing it is slim because a lot of the 5e games I've been in have more of an emphasis on RP overall. They'd probably be my go to if I was to play in a dungeon crawl game though.
I'd also love to give Shadow Sorcerer a proper try and Necromancer Wizard a chance. I don't usually play pure spellcasters unless it's Divine Soul Sorcerer because I like being able to take a hit, so even if I do play a spellcaster, I'm usually playing a martial one.
Skill: Do you prefer RP, combat, or something else? Is there a part of the game you consider yourself best at?
I personally enjoy a mix, just because of how I tend to design my characters and what sort of role I usually end up occupying. Nine times out of ten, I'm usually playing a tank of some kind - no matter what system it is (e.g. a blood hunter in Curse of Strahd whose tankiness lied in his hp, a tempest domain cleric in Icewind Dale, a dex-based investigator in my 2e game, a hilariously tanky decay domain cleric in a Fistful of Flowers, a Tzimisce in my V5 game), so by default I enjoy the combat encounters.
However I do think I'm a fairly solid RPer. I'm an ex-theatre kid, I'll commit to the bit no problem. I'm the sort of RPer who will step up when necessary, but I want to give other players - especially newer players - the opportunity to shine.
Homebrew: Do you have any house rules or homebrews you use? What are they?
I have a few specific house rules as a 5E DM:
First is in regard to keeping players comfortable: if there is something in the game that is making them uncomfortable, the player can DM me privately, and I'll end the scene, no questions asked. I've pretty much exclusively DM'd Ravenloft games, so this is important to me.
The second house rule I have is relating to the Guidance cantrip. I didn't have this implemented before, but I had a player once who abused the fuck out of it and it was not fun for the table. You can use guidance, but consider how it looks to an NPC you're trying to persuade, or how it'd feel if you're using it for stealth as it has a verbal component as well as a somatic. That might not make the check easier, but harder for yourself. It encourages a more...tactical use of it, rather than something that can be spammed. I hate that I had to do it because of one bad egg, but it was unfortunately necessary for the table's sanity.
Rule of Cool - if something isn't what'd be classified as 'strictly legal' (e.g. by the book), I'm willing to throw the rulebook out of the window in favour of 'rule of cool' for that action. I like encouraging creative thinking and want to reward that where I can. I like to offer up the potential of one free inspiration die per player per session as an encouragement for this or rp.
This is an exclusive-to-Ravenloft house rule: I implemented a system that was suggested in Van Richten's Guide for the current Ravenloft game I'm running called Seeds of Fear. I'm fairly sure it runs a little like Call of Cthulhu's fear system.
In short, fail a Wisdom saving throw (DC dependent on player's level), and I get to roll a D12 - they get a Seed of Fear. With that in mind, if they come across something that might trigger that fear, they have to roll another Wisdom saving throw. Fail that and they're frightened until the end of their next turn. This ties into the "one earnable inspiration die per player and session" rule - as if the player rps the fear appropriately