When radar positions are band boxed, the ATCO is doing just the one job. Granted that this is in a bigger area, overall, than if he is controlling just one sector, but it is still just one piece of airspace & his attention is not being distracted by events outside of his area of responsibility. But, IF an ATCO is controlling more than one aerodrome this involves him doing more than one job, & he might very well be distracted by events in his other area of responsibility.
In my view, you cannot compare band boxing of radar sectors with an ATCO doing Aerodrome Control simultaneously at more than one aerodrome.
Again depends how you utilise the technology...and equally like radar bandboxing will always still be driven by ability to maintain situational awareness and workload levels acceptable.
An ATCO in a tower now may be controlling multiple runways, including ground operations, that require the ATCO to turn their head, and be focused on one particular area...rtwr tech could allow all of those areas, along with safety nets, additional overlays etc to allow for a higher situational awareness than today, displaying the multiple runways both in front of the ATCO at the same time, rather than one potentially in a different direction in a glass tower, would mean they can monitor both at same time without the distraction, so on that principle it could be two runways from two airports.
Although in some cases multiple towers will be providing the full service to multiple airports(small sized area wise aswell as density) again it's about thinking more open, you may have a single "Air" ATCO providing runway control to two airports at the same time, while the gmc aspects may still have a dedicated ATCO for each airport. Rtwr just allows for new combinations of bandboxing, the principle is the same. Sometimes you bandbox air and gmc and gmp, sometimes just gmc and gmp, or different gmc positions...the point is in a remote tower world even those bandboxings for a single tower are likely to result in a better situational awareness as the images can be optimised/organised around the areas of responsibility an ATCO needs to see rather than the present day make do with the shared view you got.