I have an older 4GB AMD rx 580 graphics card. Realistically speaking 4gb in 2023 isn't too good for most newer games coming out and the 580 itself is also starting to show it's age. My questions were mostly related to the low vram and I'm asking them because I was thinking of buying the RE4 remake which I heard uses *a lot* of vram so I wanted to be sure before spending my money.

What happens when a GPU reaches it's maximum vram usage? The obvious would be that the performance gets decreased but is it like a "stutter" kind of decrease or am I being held back from reaching a particular fps limit that an 8gb variant of the same card would be able to reach easily like for example getting 50 fps where I could easily hit 60 fps If i just had more vram on the same card. I saw somewhere that the gpu starts looking in your system memory for more memory, and so is that bad for performance? I have 16gb of ram for context.
Thanks!

Long story short, I went to a local computer shop to ask about BF sales and asked what what brand of AMD 7800xt he would recommend. He said he didn't know because isn't an AMD GPU guy.

This got me questioning my choice to upgrade from 1070ti to 7800xt.

For those who have experienced both nvidia and AMD, what did you miss and what have you gained by the swap in terms of setup, software, interface, updates etc.

Feedback appreciated!