I have Vector 2 and like them very much.

They're down to $1,000 at REI; soon there will be a 20 % off sale.

Any power meter will work with your 520. Only the Vector will be able to tell you things like where on the pedal you apply the torque (center, left, right, etc) but that's really not important on a day-to-day basis. Might help you solve a fit issue, but I can't think of any other use for PCO. I personally don't think PP is useful either. So the Vectors will provide a lot of data to your 520 that other power meters won't, but at the end of the day what really matters is power, and any PM will supply that.

If I had it all to do over, I'd probably get a crank-based PM. I got pedals because you can move them quickly between bikes and they'll go on any bike. There are a lot of different BB standards. Then I bought a gravel bike, and Keo cleats just don't work that well in dirt and mud.