Your plan is very ambitious. Congratulations on finding a new hobby you like.

Personally, I'd definitively install only the 32 bit versions, only as virtual machines in i.e. Virtualbox, and use them to find the difference between the different distros. Only when I had fallen down on a single distro to look closer at, would I bother with partitioning, dual boot and 64-bit.

Because, you know... The task you describe is massive.