DROWN THE HERETIC BURNER!!!

It looks like power armor is going to be a limited thing this time around, something you can't use all the time and probably can't access certain features while using it. They made it more like a vehicle in this game then pieces of gear.

It'll probably bring up a Pipboy-Lite type interface. Think of the transformations from Skyrim. At least, that's my feeling on it.

Mostly, Vault dwellers do not use Power Armor. So it is probably only the SS that has this dilemma. I think it would be okay you needed to exit the Power armor to use the pip-boy. There should be "some" limitations when using PA.

Use your smartphone.

It's in the glove compartment.. you just have to lean over while your driving to access it. There's also a back panel pipboy you can operate with your butt cheeks but you need to take the "mighty buns of steel" perk to be able to do that.

well power armor is a vehicle so I'm going to guess you don't either that or its built into the hud