I have been experimenting a lot with monitors lately. I am working on and Avid S6 installation and have experienced the same issue as you have with Nuage. On S6, Producers desk only has 600mm space for a monitor. A 27" monitor is 620mm wide, so we had to split the frame to accommodate a larger monitor.
When choosing monitor size/resolution, I alway start with font size I can work with. It should not change much when moving from smaller to bigger monitor, so you can use different size monitors in your facility and Nuendo interface will always look the same, like looking through bigger or smaller window. I measure the perceived font size with ppi, which refers to scaled resolution, not monitor native resolution.
I can’t speak for Nuage, but for Nuendo 27" 4k monitor with scaled resolution of 3008x1692 (127ppi) is optimal for me, with viewing distance 50-60 cm from the screen.
On another computer I have 24" QHD (122ppi). The font size is quite similar on both. Maybe slightly small, but not overly so. High resolution somewhat compensates for wasted space in Nuendo (think new N10 Settings window, or Visibility inspector), and for some insanely big plugin interfaces like UAD.
With limited space, the 25" QHD would be a good option. With 117ppi the fonts will be about 20% smaller compared to 24"HD (92ppi). If you can squeeze in a 27" 4K monitor, than on QHD scaled resolution the fonts size (109ppi) will be somewhere in the middle between 24" HD (92ppi) and 24" QHD (122ppi). As always, with scaled resolutions you want as high a native resolution as possible.