Charlie and mac have been there for eachother since they were kids, especially mac with his codependency and "i have to do everything for you so you like me" attitude.
I like the idea of mac being trans. i think that because of the house he grew up in, his parents wouldnt have cared about getting him super gendered items in the first place because they would just get the cheapest shit possible and call it a day, in my head macs parents were largely just. absent in caring for him. obviously they did something on christmas but also thats literally macs glorified version of it in his already fucked up head. like no parent is just gonna be like "lol sorry no presents" theyre gonna pretend to care so no one gets up their ass about it.
anyways back to trans mac. i think that neither really him or his parents noticed when he began acting more masculine. him and charlie really bounced off of eachother but it was mostly mac conforming himself to how charlie looked and he realized it just made sense. i think his first haircut that was done short was probably done by his mom or dad with an extra pair of scissors lying around somewhere
as with his name, i think that he either chose it himself because he thought it would be cool (as a small child does) or, his dad DID actually name him ronald but in a fucked up kind of way where he knew he would get bullied because hes lazy and thought it would be funny. (mac also thought it would be funny but later he would realize his mistake;
in middle and highschool he received a very large amount of bullying for his voice, always getting called gay, "fairy", and other slurs that i could reclaim but dont feel like. this explains his resentment for ever being perceived as gay and his insistence on portraying himself as the most religious person possible so no one was suspicious and he felt like he would be safe being in public. this era is also when he started going by mac to atleast lessen the bullying.
he never started any real trans treatments until he was old enough to have his own job and have worked it for long enough to pay for the medication and surgery.