Do you guys mix-match your ammo in ammo cases?

Yes, but no. I use MTM cases and boxes. Each case is a single caliber, but each box in the case is either an unopened original box the ammo came in or a plastic box with a single loading in it, so there may be several different loadings in any given case. I don't put opened retail boxes back in my cases because it's too easy for them to spill out and get all mixed up, so I transfer it into reusable plastic MTM boxes that pair with the cases. When I don't shoot a full box of ammo and transfer it into a plastic box, I usually tear off the flap of the retail box that has the loading info and stick that in the plastic box with the ammo.

I'm pretty anal about always knowing exactly what the ammo I'm about to jam in a firearm is.

Cheaper target ammo goes in the same ammo can regardless of powder used since it's all for fun and relatively accurate in all my rifles.

The more expensive hunting and self defense ammo gets sorted.