If you want to clean install 64-bit Windows 10, you MUST take a full system image backup of your existing 32-bit install before doing so. And if you have that backup, and something were not to work under 64-bit Windows 10 (which is very unlikely) then you have it to restore from.
There is no way to know exactly how your machine will work with 64-bit Windows 10 without actually installing 64-bit Windows 10.