I haven't seen the movie yet, but I know I'm going to when it's released for rental.
RE: the prosthetic teeth, and how Mercury's sexuality is/is not portrayed, there are two factors I'm going to take into consideration.
Malek has a natural, tiny overbite to begin with.
As I haven't seen the movie yet, I'm curious to see if it would have been better to not use prosthetic teeth at all; similar to how when an actor can't do an accent, it's more believable to not use one at all, and let the audience suspend their disbelief. Perhaps Malek's own, natural overbite would have been enough to carry the role.
Right now, I don't understand the criticism regarding "whitewashing" (or whatever an accurate description might be) of Mercury's sexuality.
Mercury himself was not adamant about publicly declaring or defining his sexuality. Reportedly, he left the bulk of his estate to Mary Austin, who he described as "the love of his life". He often publicly distanced himself from his partner, Jim Hutton, also. Although I don't feel he was ashamed of his sexuality, I do see him as a victim of the social ignorance of the era. His fluctuation between blatant flamboyance and cagey, non-response regarding his sexuality seem very understandable and "normal" to me, given the era.
I'm curious to see if the movie reflects that understanding, and if (perhaps) the critics who view it as "whitewashing" are actually incorrectly applying 21st century standards to a man who lived in the latter, mid-20th century.