Making tracks inactive? Creating different sessions?

You could mute all the tracks with the foleys/dialogue in the mixer but much better select all the regions you don´t need anymore and mute the regions themselves or click into the trackheaders and hit mute in the track header - this way they will not be streamed from your hard drives. Then just reimport your stereo bounces like you said and go on working in the same session. If you pack the unused stuff into folders you can clear up your Arrange page.
But I would always advise to save the project under a new name (without assets into the same project folder) after reimporting the bounces in case something goes wrong.

To add to this: You can also hide the unused tracks after mmuting the regions - the hide function can be found in the track header but you have to configure it first (right click onto track header and choose hide track from the menue) then the "H" will appear in the track header. That way you can clear up your Arrange page and don´t have to pack folders.

Message was edited by: Sampleconstruct

Correct if you only mute the tracks in the Mixer they will still stream from disk (in prefader metering mode you can see the signal is still hitting the channel). Muting the track in the Arrange or muting the regions themselves will stop them streaming from disk.

Message was edited by: Sampleconstruct

Welcome 🙂
I find PT very complicated in that respect.

Muting tracks doesn't appear to function differently in the Arrange window to the Mixer window, I find. In both cases the audio is still visible in the pre-fader meter.

Only muting the regions themselves seems to prevent audio streaming from disk.

It depends on your settings in the Audio Preferences. If you set "Track Mute/Solo" to "slow" you'll get the behaviour I described.