40” @ 5120x2160 is ~139 PPI. 43” @ 3840x3160 is ~102 PPI.

Neither of these is “High DPI” by any stretch of the imagination.

If you want high dpi (particularly with macOS) you essentially need to aim for ~220PPI, the further you drop below that the worse it will be.

Personally I think the best bang-for-buck on a high dpi display is the Dell 32” 6K. I got mine for around $100 more than what Apple sells the 27” 5K (with the fancy glass and adjustable stand options) here.

If you can live with 27” there are a few choices of 5K available now/soon.