My first introduction of gzdoom runs great on potato pc recommended if you have a potato pc
It really depends on the mod/map. There are an absolute ton of GZDoom works that will grind your PC to a halt. If you don't have a particularly powerful PC, I'd actually recommend you look into the Helion or VKDoom (if your PC has support for Vulcan) engines instead as they are much more optimized for reaching higher fps than GZDoom is, though there will be some mods/maps that are made specifically for GZDoom which use features that only GZDoom currently offers, but the majority of the DOOM-based mods will still work just fine.
VKDoom is always based on the latest version of GZDoom since its keeps up with upstream code. I wouldn't really say it increases FPS and might even decrease it more if you turn on its extra features. The only time something might not run on VKDoom that does run in GZDoom is if the game/mod author is using a custom build of GZDoom of their own. VKDoom definitely doesn't help with mods that are CPU limited, which is where most of the lag of a lot of mods comes from.
VKDoom has optimisations in it for Vulcan which are not available in the base GZDoom. The plan is to eventually roll those optimisations over into GZDoom as well, but VKDoom can perform noticeably better on certain systems at the moment. Take for example the WAD "Escape Pod". My current setup is 64GB 3333MHz RAM, an RTX 4070 Super and an i7-8700k overclocked to 4.8GHz. On base GZDoom at 4K in the opening areas of the map I average about 50fps. With VKDoom it hits and mostly stays at my 4K monitor's VSynced cap of 60Hz/60fps.