Shouldn't be! I'd just make sure they smell like you since that's the most important thing

Definitely recommend the Bio Dude, he has good stuff. Giant Canyons are good too, but there a billion color morphs out there if you're into that, like dairy cows or lavas (any sort of porcellios)!

Take it slow then! Start by just keeping your hand in his tank for a while so he gets used to your presence, then after that start petting him, then work up to full pick ups. But you're totally valid, it's hard to deprogram your monkey brain, even I still get jumpscared & I've had snakes for decades

Also what kind of isopods are you getting 👀👀👀

You can supplement by giving Nib more outside time! I had the same problem with Monty but I just made sure to take her out for longer stretches of time (as much as you can with Kipper). Or you could set up the new enclosure with his current stuff until the bioactive arrive?