A 2x lens should focus on the microscope in the same way that a 4x lens does, as long as it is designed for 45mm parfocal distance. The nominal focal length of a 2x lens is much longer than 45mm, so I expect that quite a lot of low cost 2x lenses have a longer parfocal distance to make the design simpler.
For a large field of view you are more in the direction of macro photography or a dissection microscope. There is a design for a dissection microscope here: First prototype of the Field Dissection Microscope is ready to build.
Or something like this: Interesting (New?) Raspberry Pi Camera Microscope Lens
For that size of field of view you don’t really need the fine motion of the microscope stage.