I make lots of remixes, most of em Hip Hop. But I don’t do any bpm syncing with the vocals in Renoise itself. What I usually do is get the original song (with the beat and all) in correct tempo using cubase, then line up the accapella to that. That way I can both line it up proper with the beats and timestretch it to the bpm I want. Then I usually cut it up into managable pieces like intro,verse1,ref1,verse2… aso.
I did a short vid explaining the “Beatslaughter Method”, original forum post found here and the vid here. I also did one showing how I cut up samples using Cubase, but the recording software f-ed with me so it came out crap. I can make one showing how I fix up an accapella in Cubase tomorrow tho, if there’s any interest in it. Or maybe even tonight if I cut some corners hehe.