Many PC games are of course console ports. The present console generation from late 2020 both came with 16GB, but about 4-5GB of that is reserved for system/CPU use. Therefore games for those are going to be developed with a maximum of 12GB of VRAM in mind, and this should continue to be the case until ~2026-2027 when the next X-Box and Playstation arrive.
That said, the amount of VRAM required is very resolution dependent, and just about any game can run well at high settings on only 8GB at 1080p resolution. As OP has a fixed-pixel 4k monitor, 1080p is the best resolution to game at because it's exactly 1/4 the pixels so requires no scaling (each pixel maps perfectly to four)--you generally don't want the monitor to try to do any scaling as that invariably looks terrible (soft, and blurry). Less demanding games can be run at 1440p internally using DSR/VSR to do excellent scaling output to 1080p, and for that 12GB is really the minimum OP would want if they wish to play many games this way, as a whole lot of recent games use just under 12GB at 1440p with high settings (and no more even if there is 16GB on the card)
If OP wants to play any games at actual 4k with such midrange cards, 16GB is pretty much the minimum even though settings would have to be turned way down and they would have to be very undemanding or older games to be playable.
For video editing, the GPU is only really relevant when applying GPU accelerated effects, plus it helps reduce lag when displaying preview effects like in your timeline. The only feature I can think of that would benefit from lots more VRAM is frame interpolation.