The most important part is to do a separate /home partition.. in that way you will always save your personal files.

For the system (rootfs) you only need between 10-15Gb.. the /home should take the rest. A typical disk will have.

10Gb /
4 Gb swap
rest /home

In your case you will have multiple system partitions. I would go with 64-bit which normally works great but sometimes need fiddeling. Like the flashplayer which just got an supported update. Before it had to be 32-bit... which can be run on a 64-bit system. For normal use 32-bit will be enough.. you will probably not notis any big difference.

I would go with what Volt said and try them out through VM first or as i said a usb-pen. Can be tedious to do that many systempartitions. Also go with Ext4 on all partitions.. no need to use Ext3. Btrfs are to early and Ext2 is too old.

But what ever you decide.. make sure to have just one /home and mount that to what system you are using.