As a newbie, you’re probably not going to be racing for P1. It’s more important to show up with an engine that the local folks know about and have parts for, so you can get the help/advice you are going to need. The (relatively) small differences between different TaG motors will not be the main source of any lack of speed relative to the front runners. It will be skill and experience with basic things like threshold braking, correctly apexing, and just generally developing that mental database of how a kart is supposed to “feel” going through a given corner.
At 220lbs you are at a disadvantage, but I’ve seen 220 lb guys beat 165lb guys just with superior driving skill. Once you’re at the pointy end of the stick in terms of that skill, then you can worry about whether a Rotax EVO or an X125 is the better engine for you.
That said, at 220 lbs you’re probably not going find yourself on the podium at a national championship event. I tell my other (larger) buds: “Remember those guys in high school we used to push around on the football field and take to the hoop in basketball? This sport is their revenge.” All we can to is accept our fate, which is to have a bucket load of fun but no big trophies.