the bpm is saved in one of the config files in the config folder.
Right now I don't think there is a feature where you can set individual settings for different projects.
Saving each config file and replacing them each time you work on something else should be the fastest method of changing all of the settings at the same time. But I guess you'd have to restart tooll everytime.
It would be great if the developers of tooll could implement a more practical way of doing that. (For example adding those infos to a "scene" node... so everytime you click a "scene" node that is the last node of a project, bpm, soundtrack etc. could get changed automatically).
It would be really handy not having to do that manually if you switch from project to project...