Being on New IBR and RAP Simultaneously for different loans?

My understanding is you can't be on RAP and a different IDR plan like New IBR for different loans at the same time.

Reason I ask is that I have Grad Plus loans that I want to start paying now and will be enrolled in New IBR. For my Direct Loans I have to consolidate them to waive the grace period and that will put those loans presumably on RAP (even though I'll select New IBR when I submit the consolidation application). It is my understanding that because the consolidate loan will be on RAP my other loans will need to be on RAP as well.

If my other loans need to be on RAP as well, how long will the process take from going from New IBR to RAP? Will it take on the order of weeks like a traditional payment plan switch or will it be days/automatic? Recognize no one might know but wanted to ask if that makes sense