Do you aggregate your USB audio devices, or use a mixer?

I have a USB mixer, an Octatrack, and an OP-Z, plus a guitar.

Sometimes I plug the OP-Z’s analog audio out into the mixer, sometimes I create an aggregate device and use the OP-Z and the mixer together, using Rogue Amoeba’s Loopback.

The aggregate device approach is very convenient, but creates extra latency.

Do any of you have preferences or tips?

I used to aggregate a MOTU UL Mk3 and a Novation 2x2 soundcards under Mac.
Have been doing it also with the MOTU and DT and it works fine.
Not able (and not interested) to measure latency. As long as 1 of the 2 is being corrected for drift in the Mac preferences, it is fine.
Don’t use aggregate devices anymore as I have downsized my setup and REC only stereo outs into the MOTU or via DT INs.
I believe it is a whole different story under Winx regarding latency.

opz is not the best at aggregate devices … have to reset many times latency in 1 hour session … don’t know from where it comes (unstable drivers ? )
in other hand it works well with model samples and digitone (no opz) ,no latency between them.
so it depend on devices

I don’t care about latency unless I’m playing guitar, and then I have to switch to a single interface or it’s hard to play.

My favorite way to combine USB audio is overbridge. No added latency there, and as many OB devices as you like.