Dan I will be the bad guy.
If you're trying to line up computer-based (on a grid) tracks with a live performed track you have to use a "tempo map".

The only other option is you can have the live performance aligned to a grid through extensive quantization but then you'll lose the live feel.

There have been advancements in tempo mapping over the last five years.

"Logic" if you're on a Mac can do it automatically.
Melodyne can find a detailed tempo map for you but it's another long process. Free version limited. Paid version detail process but very accurate.
Other DAWs have gotten better at it to cut a twenty-minute process to a five-minute process.
I am not sure of the state of the art in Reaper, but it has gotten easier in the last 10 years.
BIAB, can also find the tempo map with their ACW. Not sure how to get it out of BIAB, maybe a MIDI file with tempo map in it.


Studio One (latest version), Win 11 23H2 , i9 -10940X 3.3 GHz, 32GB Mem, a 4K 40" monitor, PreSonus Studio Live III Console as interface/controller. secondarily test on Reaper, Cakewalk, and S1 on Surface Pro 3 Win 10 (latest versions).