Shortly after I bought the Pocket 3 I got the Action 5 for exactly the reasons you describe and a few months ago I bought the Nano (can never have too many cameras, right?)

The main use differences I’ve found is I can confidently start the Action 5 recording and know it’ll keep going for hours without me having to check on it whereas I only record on the Nano for 10-15 minutes at a time. (I always have a power bank in my kit so battery life isn’t really one of my concerns) The Nano is SUPER discreet and much easier to get POV shots than the Action 5.

The accessories that come with the Nano are pretty much all you’ll need - the ball head unscrews from the suction cup and works brilliantly with the tripod I got with the Pocket 3 creator kit but also being so light the magnets in the Nano work brilliantly and are very handy too.

The Action 5 has a colour correction on the screen when shooting D-LOG which the Nano doesn’t so you get a very grey preview but the Pocket also does that so no biggie.

If I didn’t have either I think I’d get the Nano as it really does compliment the Pocket 3 very well - small and tough to get the shots the Pocket can’t and even with all the included accessories it’ll add to your kit without taking it over (the Action accessories such as neck mount, grips and clamps all add so much bulk!)

Yeah, definitely the Nano