I found that the best set up for me was to use a pair of assioma duos as my main/single source of power. I use them to power match against my Tacx neo 1 indoors and then I’ll take them off to put on my road bike outside. I found that at high fly wheel speeds the Tacx neo would give fairly high power readings - perhaps 10% higher than my duos. At low fly wheel speeds I’d see the Tacx was around 1% lower than the duos (spot on in terms of accuracy).
I also have a gravel bike with a quarq dzero on. After plenty of testing I adjusted the slope on the dzero so it was a better match to the duos. I’m not sure which is more accurate but I’m happy to go with consistentcy.
My advice would be to consider pedals as your power source. The they take a matter of seconds to swap over and would give you consistency between indoor and outdoor rides