Sometimes when I want to do another build, I’ll spend a bit of time farming on my higher level character to grab some key pieces first. Am I any less likely to find what I’m looking for if I’m farming on another class? Either affixes or bases?
There is a system in place called item affinity.
It only affects non-unique/set items and only a portion of some item types.
Over all the system is not that much impactful and you can essentially farm anything on any char basically.
I would say the exception is idols. These do seem to drop almost only for your class, I feel like I get idols for other classes only from shrines, and perhaps monos rewards, never in random drops.
For all other items I don’t really feel the difference, anyone can farm anything.