A guy called Tim Staffell was the singer in a band called Smile before Freddie Mercury joined it and it became Queen. There is an interesting interview with him in Esquire.
My departure from Smile was completely amicable. I began to want to play music that was more improvisational. I was drifting towards listening to jazz and blues. The movie has used artistic license to depict the departure, but it wasn't really like that because Freddie and I were good friends at college. (We were in the same year at art school. We were taking the same course.) Freddie joining the band was very natural, as he was really good friends with the band members before I left and simply dovetailed in. I just said to them, 'Look guys, I've already gone for some auditions,' and I said, 'I'm not happy with this anymore and I don't think it's gonna work out.' How wrong could you be?According to Staffell, Rami Malek's performances captured the nuances of Mercury that he remembers. "Wow, he has done his homework so much that he's dropped into character by observation. He's serious about pulling this off".
Who do we think is likely to be the best judge of an actor's Freddie Mercury, Staffell or Collin?