so ive been trying to understand how boss immunities and resistances work, and what level resistances bosses have in general.

I read somewhere the -phys and-magic kind of work like an aura for yourself, lowering the resitances of bosses.

But how much do i need? Do i need an amp + the -phys to peirce?

I heard mappo has 250 physical resistance, would i need 250 to pierce it then? or 260 to start doing damage? or do I need an amp on him + the -phys on gear?

also whats the resistances of the end game puzzle bosses trag and ctoggha? I know they cant be cursed with amp, so is it possible to actually kill them with just phys?

i would appreciate if any veterans can explain this to me!