Arrange windows in 8 tiles on Win 10
Solution 1:
Microsofts own PowerToys (i.e. FancyZones) can be used to tweak the Snap behaviour and achieve exactly what was requested.
Solution 2:
What you are looking for is called Tiling Window Manager
There are number of examples on that Wikipedia page. Perhaps a better list can be found here.
Can't recommend a specific one, as I am the developer for one of them, and, obviously, biased :-D