The multi-monitor support in Windows has really come a long way in the years that MaxTo has been around. With Windows 10 and MaxTo, the multi-monitor support is brilliant.
When you set up your regions; MaxTo will show the region divider screen on each of your monitors. Each monitor will have its own set of regions, and you can choose to only set up regions on some of your monitors.
MaxTo supports multiple monitors running at different scaling settings, known as per-monitor DPI awareness. This means that it should be trivial to connect your 4K laptop to a stationary full-HD display, and things should work exactly as you expect.
We strongly recommend running Windows 10 (and keeping it up to date) if you have monitors running at different scaling levels. This is because Microsoft's support for mixed-mode DPI scaling has been mediocre at best in previous versions of Windows.