As someone who's been really interested in Taoïsm and who can experience flow quite easily likely die to ADHD (but also really hard at other times) I wouldnt call them comparable.

Flow to me, is what others already described as doing something where my mind is just finally shutting up for a second.

Wu Wei to me is much more mindful. By being in the moment consciously and surrender to that feeling so everything you do because somewhat flow like. Instead of thinking "i have to do this, call that person, go for groceries etc" you just do this and only this. Thereby you can correct yourself as well if you notice it and stay in the flow state.

Whereas flow to me means completely disregarding a ton. Normally I notice almost bloody everything, but when in flow I just have all my energy focused towards the activity.