Real Band uses the same chord grid Biab does. Since you're starting with a midi file and then need to "play with the chords" anyway, start in Real Band in the first place. You just go to file>open and find your midi file. One big thing that RB can't do is create a Biab midi soloist part. Note I said midi, RB will create a Real Track soloist just fine.
There's lots of little tricks you can do in RB. For example, everybody knows you can put in part markers in the chord grid to force a drum fill. In RB you can create a drum track but then change the chord grid to put those part markers in different places and create a completely different drum part on a different track. You can do this many times using different part markers for each one to get different fills in different places. Now, do that with different styles.
RB will only generate the tracks you want it to, everything you've already done stays unchanged. In Biab, if you change a style or the part markers and regenerate, everything changes unless you've frozen some tracks. Freezing tracks is ok but why not just start in RB where, as the project evolves, you're probably going to wind up anyway? If you're like Silvertones jazz guitarist friend and all you need are some cool sounding backing tracks for a restaurant gig great, Biab is perfect for that. You don't get all the neat little song specific fills, punches etc but for a live gig, who cares? But, at home trying to create either a good cover of something or an original with specific parts in it, Biab won't cut it. You need the 48 tracks, access all the different midi synths you may have and output ports, the ability to create multiple Biab working tracks in order to finalize one good one, bring in some midi tracks from several different sources, all that kind of thing.

Bob

Biab/RB latest build, Win 11 Pro, Ryzen 5 5600 G, 512 Gig SSD, 16 Gigs Ram, Steinberg UR22 MkII, Roland Sonic Cell, Kurzweil PC3, Hammond SK1, Korg PA3XPro, Garritan JABB, Hypercanvas, Sampletank 3, more.