I don't have a tomini but I have read quite a few post if them being pretty aggressive, just depends on the fish. Whatever you decide have a plan if one needs to be placed in timeout.
I gave up on powder blues after the third try as I can't keep them alive. Last one I ran through 30 days of Copper and within a week of being placed in the display it died of ich (as all previously did) and not a spot on any other fish including 4 other tangs.
Just for info. I have a purple, hippo, convict, naso, and yellow together that have been with me for quite a while and are pretty large and I have zero aggression. In another tank I have a yellow and two spot bristle tooth and the bristle tooth is starting to show a slight amount of aggression toward my CBB and tail spot blenny.