What’s the difference between 32bit and 64bit versions?
The 32bit version is designed for both 32bit and 64bit Windows systems, the 64bit version is only for 64bit Windows.
There is no significant difference in the speed of the program on either system. The difference concerns the memory resources that the program can allocate for loading and editing a drawing, in particular a drawing containing bitmaps of large size and density, where large resources of available memory are especially valuable for smooth panning or resizing the presentation of large formats. Thanks to the virtual image of the entire drawing format in a given precision, all drawing display operations are many times faster than the same operations with the virtual image option turned off or impossible due to limited memory, but the memory resources for creating a virtual image are the greater the larger and denser the bitmaps are and the greater the precision of drawing is set.
For 32bit version of AlfaCAD, the memory limit is 3GB per program instance, 64bit allows you to address and use all the memory your money can buy.

AlfaCAD for Linux is 64bit application for modern Linux system, preferable Arch Linux with KDE, however it can be ran on any Linux distribution with either KDE or Gnome desktop environment.