Silyavski I'm struggling to understand exactly what your asking but I will try to help.

If your unsure of the correct screw to buy then to answer correctly would need more information about machine size and use.
Generally for small to medium sized machines (1200x1200) then RM1610 is perfectly fine. Over this then look towards RM2010.
The 10mm pitch works good for most types of cutting inc aluminium but if your wanting better resolution rather than speed then consider 5mm pitch. Or if using timing belts to attach motors then gear 10mm pitch 2:1 and increase torque and resolution at the cost of speed.

Regards choosing the ballscrew for being on same plane I'm not sure what your meaning because the ball-screw ends have to be on the same plane has does the ballnut mount otherwise they won't align and stick.? . . . . I Understand English is not your native language but please try to explain better.?