I’m assuming (given the text in the post and the community) that this is for gaming purposes.

Well, the simplest is going to just be “reduce the high-level settings in the game until you’re getting acceptable performance”. Most games will have presets (“low”, “medium”, “high” or similar) and while technically some of those settings probably aren’t limited by VRAM, it’s probably also a reasonable bet that the card is going to be performance-limited in other ways, since it’ll also be older.

If the game has an in-game FPS monitor, turn that on to help you get a feel for the impact of flipping a given switch. If not, Steam’s overlay has its own FPS monitor if you’re using a Steam game, and mangohud can provide another.

Then if you want to try to pull more out of the card, most games have individual high-level settings. Go through and bring up individual settings on each, checking if you’re getting unacceptable-to-you framerates.

If you hit some point in the game where you’re seeing slowdown, drop into the settings and cut the quality options until you do get a reasonable framerate.

Some games have mods that will let one disable even more chunks of the game than the developers intended, though I probably wouldn’t spend much effort on that unless I were really determined to play a particular game.

There isn’t going to be a lot of general purpose, no-tradeoff “just get more performance” switches; if there were, developers would have flipped them.

You can try using gamemode.

https://github.com/FeralInteractive/gamemode

GameMode is a daemon/lib combo for Linux that allows games to request a set of optimisations be temporarily applied to the host OS and/or a game process.

Your Linux distro will probably have gamemode and mangohud packaged for you; they are in Debian.

Some drivers will have experimental options to try to eke out a bit more performance; typically these are not entirely stable or have bugs on at least some cards. Under Xorg, one threw these in one’s Xorg.conf. I’m sure that there are still similar options in Wayland, but I couldn’t tell you how to toggle them off-the-cuff. Might be all kernel command line options these days, as the kernel hands more video card interactions than it did last time I was mucking with this. My experience has been that it’s generally not worth the effort.

EDIT: If I were running on a 4GB card, my first move would probably be just choosing games that don’t do much with the GPU, if those are genres that you like. I mean…I’ve gotten a lot of enjoyment out of Caves of Qud. That does very little with the GPU, says that anything that does DirectX 10 or above will work fine; the RX 6400 looks like it has DirectX 12 support. Same for Oxygen Not Included, which requires DirectX 11 and recommends 2GB of VRAM; I was just playing that today. Not really making any tradeoffs on those.