stealing speed is pretty common for contemporary speedsters, Godspeed and Barry also know how to speed steal; stealing speed was a major plot point for Godspeed's introductory arc.
as for Wallace being faster or more talented than Bart and Wally at his age or when they were in the Kid Flash role, I don't think DC's ever done anything with Wallace that would indicate that. As a character, Wallace has made great strides and has become pretty fun to read, but as a speedster, they've never done anything all that impressive with him. In fact I'd even go so far as to say, despite DC nodding to him having "potential", Wallace has consistently been portrayed as being on the lowest tier for any of the prominent speedsters and could actually use some legitimately impressive feats to actually demonstrate what this "potential" of hs is.