[Sangeppato]

That's weird, reliable low latency audio is one of the few things where I still find the Mac to be pretty solid. I've got a 2015 15" and I've used several times a 2018 13", on both Mojave and Catalina and I have to say that it outperforms my 2015 (it can easily manage a 32 buffer with some plugins loaded, while my 15" starts to struggle under 64). This was using Reaper with an Apple USB-A to USB-C adapter and a UMC204HD interface

[rednum]

I use Ableton with Focusrite Scarlett 2nd gen. I'm currently using 256 buffer. I've tried using 128 but it screwed up some vocal takes I did the other day (there are 5-10 seconds of cracks in the middle of each 4 minute long complete song take). Also I froze the other tracks (eight of them, so not that many) before starting recording. No FX on master track.

Maybe I should've bought 2015 MBP then. Or maybe I should downgrade to Mojave? Or buy the Apple adapter? Or a different interface? No idea; both Focusrite and Ableton say they are compatible with Catalina.

[Sangeppato]

As I've said, the 13" 2018 I use from time to time can easily manage a 32 buffer, even on Catalina, so your device should be just as good.. My suggestion is to try with a different adapter and maybe with a different DAW such as Reaper, just to double-check (although I don't really think the DAW is the issue here). It may also be related to the plugins you're using, maybe they're just heavier than mine..

[PascLeRasc]

I'm on a 64-bit buffer on Catalina/2015 Macbook Pro/3rd gen Scarlett/Ableton, just as a reference point. Sorry to hear that.