RE: AXI 2208/26 motor questions...........
Your motor is rated for max 11A.
With a 9x4,7APC-SF propeller on 2S LiPo the load will be appr 12-14A I think. Too much, but it could fly for years without being damaged as long as the cooling is good.
Your 3S620 batteries should not be loaded at more than 9A, absolute max. I think a 6x4 already is above that on 3S...