I’m against wall units as they aren’t the easiest to use and aren’t that big.
Consider making one wall of the kitchen full height floor ceiling units and you get double the wall unit depth plus the additional height.
I originally looked at a single large unit and they are available, the issue is the 250mm connections, going to the outside with that size and then splitting it into 2 and then into your plenums, you will need 2 plenums each for supply and extract for a house that size, I have a pair for downstairs and a pair for upstairs.
The issue at running these units at these speeds is noise and efficiency. At full tilt they do make noise that will then be transmitted through the ducts to some extent, and if you look at the details they are far more efficient (heat exchange) at around 50-60%. PassiveHaus specifications don't allow them to run at those speeds, a PH certified unit has a lower PH capacity that it's absolute capacity. My Brink Renovent 400's run at 140 and 175 m3/h respectively, they are capable of 400 m3/h but as you go above 200m3/h they start to become audible.
All the quotes I have specify 2 MVHR units, having looked on line, the majority of units are for homes up to 150m2 floor area. As I have a large plant room and wondered, is there anyone manufacturing a large capacity single unit ?