As to "2. My matches should have the same ethnicity that I do", I think, in general, a match is an indication that two people are identical over a considerable portion their genetic makeup. Therefore, their ethnic affiliations should be similar because it's based on the same sample of genetic markers that produced the declaration of a match. Yes, in each generation there are random combinations of genetic material from two parents and there is considerable potential for cousins to genetically "drift" apart because the genetics of their common ancestor, by chance, don't get passed along. However, if this happens, it reduces both the likelihood that they will be assigned similar ethnicities and that they will found to be genetic matches. The two are inextricably related, aren't they?