[selectnull]

That depends on the size. For 27" or larger, the recommened resolution is 1440p (non-retina) or 5K (retina). 4K is ok if you're going for smaller sizes.

More information here: https://bjango.com/articles/macexternaldisplays/

Just recently bought 27" Dell and I'm quite happy with it (for coding).

[msencenb]

Which dell did you end up going with?

[selectnull]

Dell P2723DE

[JSDevOps]

What’s the refresh rate on that?

[selectnull]

60Hz

[JSDevOps]

This is a similar monitor at a similar price at least in the UK but it benefits from the 120hz refresh rate

Dell UltraSharp 27 Monitor - U2724D

[msencenb]

Thank you, great resource