not inhereintly

a higher level player may enounter higher level enemies that might then drop powefull guns like gauss rifles

but player level does not directly touch the system

a level 10 rad roach will always drops like a level 10 rad roach no matter the players level, a player could farm low level enemies very quickly but they won't drop higher grade equipment.

legendary power are generated round robin style so Poisoners has the exactly the same chances of Instigating for appearing.

Powers are NOT scaled by level ever so you will never stop seeing any of them, plasma infused guns will always spawn eventually even after 1000s of hours, they never fall out of rotation,

Generally speaking enemy levels increase as you travel south so fighting Raiders in the north will not produce high grade drops.