Yeah, beat me while typing.
The various behaviours of different kinds of tracks can be confusing.
In this case, unlike the MIDI track, your recording has no data that will cause it to follow the project tempo change. The grid moves relative to the audio clip and wave form but the sound doesn't change, right?
There's probably a bunch of ways to do what you want, here's one suggestion to get you started exploring. To prevent inevitable mistakes from corrupting your project, I would suggest an experimental/practice attempt first.
Mix down a copy of the tracks you wish to play along with. This could be a few, or all the tracks in your project, a portion or selected measures, many options. Lets keep it as simple as we can and just make a copy of the song. Create a new project with a new name for practice, and import the new audio track.
Next step, making sure we can return from time travel to the same spot where we were before. Note the tempo
and slow down the track tempo in the sound tab until its about where you want it.
Arm a new track and record your guitar. When satisfied, edit the new clips tempo back to match the starting point.
I think that will help get you started....... Not where I can test and verify, but I think I got it right.