To my exprierience, the order of installation doesn't matter.
I usualy install in the following order:
- Main Programm, bandinabox_realband_2016_pluspak.exe (in your case)
- additional pak's like *_8pak, *_49pak
- all realtracks

Somtimes I start another realtrak-exe even bevor the one running has finished and also sometimes parallel to different locations like installation localy on drive D: and parallel to an external drive.

No problems so far.

When installing parallel onto 2 different drives you must be Aware to type the corret drive-letter for every *.exe you start.

Regards
Thomas