gcw I think there’s a couple of different questions here….
Mixing from (for example) a track at 122bpm to one at 125bpm should be fine. With a very few exceptions, I tend to play my records at no more than +/- 3 or 4. Occasionally you’ll find a track that sounds great pitched down a whole bunch, but I typically find the producer pitched it where they did for a reason. A couple of bpm either way I find doesn’t make too much of a difference though. So if you’re set is rumbling along at 125bpm, and your records are mainly between 122 and 128, you should be fine.
The other question seems to be more about changing the tempo of your set during the set. I think this is a lot trickier to do in a recorded / home listening format than in a club, where you can get away with a lot more. If I want to raise the bpm of the set, I tend to aim for a track that’s got a breakdown, and particularly one where the energy of the track lifts at the drop at the end of the breakdown. Apart from a 12 hour marathon though, I’m not usually raising the tempo all that much during a set - maybe a few bpm, but not usually much more than that…
