Been looking into this more. I can use 5x optimized modes on PAL consoles (each tweaked to their own).
I tested 4x optimized on PAL with my PC monitor and it did work but with the cutoff that occurs on PAL. On compatible displays, increasing the V. Active to 270 can fix this but on my TV, this isn’t an option.
Going through my N64 games, the following games are unaffected by cropping
Wave Race 64
Super Mario 64
Duke Nukem 64
MArio Kart 64
The following games have workaround in the form of letterboxing
007 The World is Not Enough – Activate Hi-Colour mode
Goldeneye 007 – Use Wide or Cinema screen size
Perfect Dark – Same as Goldeneye 007
Army Men – Sarge’s Heroes – Use letterbox view mode
So as always, it is dependent on the display with PC monitors and 4k TVs more likely to cope.
Just to note, my PC montitor will not accept 5x from a PAL console but my TV will.