Hi I hope somebody can help me! I’m looking to buy Wheels for my car. I want 19” in the front & 20” in the back. I have seen it and it looks good. But I just heard that it’s not good for the car to go with a bigger tire. What do you guys think!!

Basically the VT system is designed to have both front and rear tires turning at the same ratio. In perfect harmony, wear on the tires, clutch etc is minimal, not to mention power loss. Different wheel sizes upset this balance causing..... well an unharmonious union

Welcome to the board

As long as the total outside diameter of the tire stays the same.
My 91 Diablo as 335/35/17 in the rear. For me to go to a 20" wheel I would need 335/25/20 size tire. The original is 26.23" tall. The 20" rim tire would be 26.59" tall. A little more that a 1/4" taller is fine.
How do you find the height of a tire you ask?
I'll do it on my original tire.
335 multiplied by .35 = 117.25, then multiplied by 2 = 234.5, then divided by 25.4 = 9.23, the add the height of the rim (17") = 26.23
Remember a thinner sidewall would give an even harsher ride. (if thats even possible in my car LOL)

Let me reiterate. A larger diameter RIM is fine. As long as the total height of the TIRE remains the same. So as you increase in RIM size, the side wall of the TIRE will be thinner.