I have a MacBook Air 2020 that I would connect via USB-C. I also have an HP business notebook that I would connect via USB. Does this constellation work with an MX Keys keyboard and MX Logitech mouse? Can I control both notebooks with this keyboard and mouse?
Has anyone already used a similar constellation?

It is only relevant whether the graphics card of the connected device supports the 3480*1200 mode of the monitor. Under Windows, this can be found under Display settings => Screen resolution.

We have connected the monitors above the docking station, but I don't know if it works without.

We have a MICROSOFT Surface Laptop and a Microsoft Surface Laptop Go Business connected to a Samsung SyncMaster C43J890DKU at our company. This works without any problems and the resolution is also very good.