Seperate power for 3.3 and 1.8 rpi4

So after a whole lot of searching, I have found people saying they have replaced or bypassed the switch mode regulators for 3.3v and 1.8v on the rpi with linear power. I cannot however for the life of me find any info on exactly how to do this, i.e. what regulators have to come off the pi and where to solder new 3.3v and 1.8v power.

This would be done on a rpi 4b. I would like to take 5v (3.5a) linear power, and use linear regulators to step down to 3.3 and 1.8v from the same 5v source, as well as passing 5v from the PS to the pi. Would having it setup this way cause some weird ground looping? I know just enough to get me in trouble, so any advice is welcomed!

More searching, is this even doable on the rpi4, since it uses MxL7704 for power management? Would it even be worth the effort?