"Upgraded" from a GT 730 to a GTX 1050TI but somehow worst?

So to make this short, I once had a GT 730 that could run games but I mainly use it to play Roblox Forsaken. It can handle the game decently well and smoothly without that much problem. However the GPU broke so I had to use an AMD Radeon 7600 temporarily (which can't run pretty much any games if it's not Minesweeper lol) until I got a better one. The repair shop guy ended up reformatting my PC for some reason and about 2 months later I finally got a second hand GTX 1050TI!

It was doing good, I tested some heavy games and it went well(40-60fps average), but when I played Roblox Forsaken I noticed that the game frequently stutter and stuff. At first I thought it might be on Roblox or Forsaken's part so I tried other games on Roblox but some stuttered and some didn't!

I was confused as to why my GT 730 could run some games that my GTX 1050TI can't.

Also I noticed that sometimes a rainbow line would appear in the middle of the screen and sometimes the screen would turn black. Maybe it's a GPU problem.

I tried so many tutorials on how to stop stuttering on Roblox but nothing worked, I'm starting to think that the GPU is the one at fault.

I wanna know why that's the case?