Can someone confirm the best setting for bridge stp. None? Or the other two?
TLDR: It doesn't matter here
Bridge STP almost certainly has nothing to do with this situation.
Spanning tree is a protocol that is designed to allow redundant connections between switches and one link is automatically disabled until the primary link loses connectivity. The parameters all have to do with how the primary link is chosen and which link is a backup link. If this is just at a home installation and there is only one connection between ethernet and any other switches, then you are safe to just disable STP entirely.
In any case, STP doesn't affect the speed of throughput, regardless of the mode. Any changes in throughput on wireless when you changed STP settings are a coincidence unless your device is so close to 100% cpu that the last bit of resources required to run STP put it over limits....
As for the wireless performance - all I can say is that for some reason, I've never had as good of a wireless experience with a Mikrotik AP as with other vendors (especially Ubiquiti). I love Mikrotik, but somehow I feel like wireless is hard to get right with them and "it just works" with other boxes.
As for routing / bridging / tunneling / etc - Mikrotik is fantastic beyond words. I just haven't been impressed with them as a 2Ghz indoor AP. (point to point outdoor bridging works great with them, though)