RB 2015 can use 64bit VSTis, and VSTs. So that is not a problem. I have track several projects entirely in RB. I seldom even use BiaB anymore. I find RB does 90% of what BiaB does in simply generating basic tracks for a song bed. I mix and process them right there. If i run into a situation where i can't get RB to do what i want i have Presonus' Studio one Pro where i can do what ever i want.

SIde note i was noodling around in Studio one last night, and trying different sampler sounds that come with the program. I was messing with a drum track that was basically a midi file i downloaded. I ran the file through EzDrummer, which is so easy in SD1, all one has to do is drag the VSTi onto the track, and a box pops up and asks "do you want to replace what ver synth it is using" Which in my case was their "Presence" sampler. Then i opened up EzDrummer and set it to multi output, and in the track inspector in SD1 their was a drop down arrow i opened it and it has check boxes for all the outputs of EZD. check each one and a track appears for each. Add effects to taste and mix down. Very cool deal.

HP Win 11 12 gig ram, Mac mini Sonoma with 16 gig of ram, BiaB/RB 2026, Reaper 7, Harrison Mixbus 11 , Presonus Audiobox USB96