Question

Can the beat vary within a song and keep the measure count the same as on the score?

Answer 1

It depends. While the beat might vary between songs, the measure count might often change as well. Different beats have different measure and tempo counts as well as different loops & instruments. I haven't used the program's loops that much yet to be honest but more like it's MIDI editing/making feature. I hope someone else can give you better answer.

Answer 2

All the elements you mentioned can be easily considered as variables that change based on each other. Yes, you can have the same beat for a song or you can have two different BPM, but other elements will change as you modify or increase the BPM. If you try to keep one value and change another, then the result won't be what you expect. For music and notes including beats, everything must be in a "symmetry" or you'll end with a totally different track.

For example, if you change tempo in a song, then other variables will change as well.