@rrfitness For sizing, here's how I'd pick:
1) First decide if you care about getting a Tesla OEM tire with the foam liner. If you do, then for 20" wheels on a Model 3 it'll have to be 235/35R20, there are no other Tesla OEM choices with the right outer diameter.
2) If you do want OEM Tesla spec foam liner, then for 20" on a Model 3 your only options are the Michelin PS4S (original M3P OEM tire) or Pirelli PZ4 (what newer M3P come with). Between those it would be an easy choice for me - I'd go for the PS4S over the PZ4. I haven't used the PS4S myself but friends I trust have and say they're good, and they're also widely regarded as a better tire on these forums. The OEM PZ4 were kind of mediocre in my opinion, I felt like I wanted more grip (and I got it with the Potenza Sport).
3) If you don't care about OEM Tesla spec (foam liner), then I'd say next decide between Potenza Sport or PS4S (assuming you're focused on ~ 300 TW "max performance" category). I don't think there's a wrong choice between them. My guess is the Potenza Sport are slightly more responsive, while the PS4S ride slightly better, but probably not a drastic difference either way, especially not in 20" sizes with ultra short sidewalls.
4) If you decide Potenza Sport, then for the OEM 20x9" Uberturbine wheels I'd go with either 245/35R20 or even 255/35R20. I would *not* bother with 235/35R20, that's weirdly narrow for a 9" wide wheel, you can even see how the OEM PZ4 are stretched in that size. Normally I'd go with 255 for 9" wide wheel BUT 255/35R20 is pushing the limits of rubbing the front knuckle in this car. From reading these forums, some tires fit in that size, but others rub. I think *typically* it's allseasons with their taller tread that rub, but there's still a risk with summers. So 245/35R20 seems like a safer bet.
5) If you decide PS4S, I might lean slightly (just very slightly) towards the Tesla-spec 235/35R20. Supposedly it's wider than a regular 235/35R20 especially in the tread. But if you specifically don't want the foam liner, or can't find the Tesla spec in stock, then I would go for either 245/35R20 or 255/35R20 for regular PS4S. Same caveat as above with 255/35R20. I'd probably just get 245/35R20 to be safe but really up to you, some people have had success with 255/35R20.