Like you wouldn't believe. Expect people to have built cheats for this game before it even comes out that will let them teleport to your position, instakill you, take all your items away, teleport you to a remote location on the map, turn you into a fucking mole rat, force your character to dance or perform a dick sucking animation, literally whatever. It's going to be fucking magnificent. Honestly even if they implement some simple cheat detection after this point it's going to suck and be easily worked around.
Edit: this is NOT optimistic I'm telling you people have
already ported fallout 4 mods into fallout 76 in working condition, all of what I just described will be trivially easy for modders to pull off if not already by launch then within a day after it.
THE GAME DOES NOT EVEN KNOW WHEN YOU'RE CHEATING LOL.