If you use it at “native” 2x yes. A 24” 4K looks better at 2304x1296 IMO, and a mini will drive one display like this fine, provided you have enough memory.
To me having non-iCloud data on an external drive is actually a bonus because should you need to take it in for repairs it’s just unplug, get a spare/loaner and you’re off and running again.
There’s plenty of choices to suit any aesthetic/price/performance issues. For home users the owc mini stack is probably a good choice.
I'll probably change to 2x 5K + my current 27". So I do need some more GPU-power. Would be great if there were some TB3 cards on the market that are compatible with the 5,1 ...