I’ve been down this road. It can get expensive in a hurry. Indoors, I use my trainer’s power which allows me to take advantage of ERG. Outdoors I use my vectors. As far as differing goes, it’s not a big deal to me. I’m only outdoors from March through October, then Suffernate during the winter. So I just retest to set my 4DP using the PM I’ll be using for that season.
Here’s my post where I discuss my rabbit trail
Power meter inaccuracies