Basically, tint will just slow down the heat buildup for the most part. Given long enough in the sun, the car will heat soak and get hot. I have 15% ceramic tint on my side windows, 70% on the front windshield, on my S, and a tinted roof, and after about 4-5 hours outside, the car will be in the 120's+ here in Texas.
It does help when driving the car a lot as I definitely use less energy for the AC than before. Still just living it out, it will heat up but the tint does slow it down. Mostly noticeable if I run into a store for about 30-40 min. The car isn't near as hot when I come out.
As a side note, on days that I see 120-125 internal temps, were about 145 before and after the same amount of time outside. By 5-6 hours in the un the car will be really up there. As a point of comparison, I parked my 3 (totally untinted but a fabric sunshade like Yeslak but without the inner reflective mat) next to my totally tinted S. Both started the day at 90F. By lunch (3 hours later) my 3 was at 125F and my S at 105F. My 3 peaked that day after 5 hours at 150F. My S hit 128F after 6-7 hours. So while a definite improvement the car was still hot AF inside. Not a complete apples to apples comparison as the S has a bigger cockpit and more glass along with a hatchback. So while the tint did help a lot, it doesn't overcome everything.
What makes the 3 even worse that the terrible high temps, is the lack of ventilated and cooled seats. A huge oversight on Tesla's part. One of the main reasons I hate driving my 3 on hot days. The plastic seats in the 3 just cook you when you get in.