I run 2 Dell U2518D displays, they're QHD/2560×1440 and they look terrific, running them at native resolution. Since these are 25" displays, the PPI gets enough of an increase that's it's pretty noticeable over a 1920x1080 of the same size, or a QHD at 27". I find these size and resolution a pretty outstanding mix of: screen real estate, pixel density, price, as well as, being a good match for the Mini in terms of graphic processing (i.e., everything is perky).
I use this machine for general / personal computing, development/design, running VMs / containers.
Oh, FWIW, I'm running both of them off the TB3/USB-C ports via USB-C_to_mDP adapters, and the mDP_to_DP cables supplied from Dell.
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Oh yeah, I'd also say, that I prefer having two displays vs. one larger one, I kind of like splitting things up across physical monitors, and for some tasks, I like being to go full screen (a VM, remote session, etc.), while having another display still fully available. I also being able to position them independently, I keep them turned slightly in so I'm looking at them more straight on (if that makes sense [?]).
Hahaha, and this might sound silly, but I also like being able to see between them, vs. being behind a wall-o-display.