You can override the behavior by adding efi=runtime to the kernel options.  PREEMPT_RT kernels have this off by default in their config files due to the above mentioned measurements.  My concern is that once everything is loaded by EFISTUB exactly how many EFI function calls happen in the course of using the system and how would that affect realtime.  I'll report back if I find any negatives.

As for your DAW issue, all I can say is that up until 4 days ago, I was running a 1050ti with the nouveau driver and the rt kernel with no xruns when using guitarix.  I don't record so I can't really speak to that as my issue with nvidia cards.  I could never get their nonfree driver to load but didn't worry about it too hard TBH.  I got a decent bonus this year so I just got a Radeon RX 6650 XT last Thursday because I couldn't do blender without significant frustration and needed it to do CNC with.  The blendercam plugin is fairly decent and, once you learn a few vagaries, blender puts freecad to shame.  I'd say my advice would be to ditch nvidia as amd seems to give a damn if it's at all possible for you.  My new card cost $310 but it was well worth it IMHO.  It's a XFX Speedster QICK308 Radeon RX 6650XT if you might be wondering.