Swapping from Raid 5 to Raid 0..easy?

Yes this means raid0 or better with a RN104, JBOD. raid0 is meant to be faster by using several disks, but JBOD copies on one disk at a time, still giving you the full volume size and with decent disk you will still get the full speed of the NAS, but if one disk fails you lose only what's on that disk. With raid0 you lose it all.
Anyway, you have to backup your data to another physical device to be protected from disk failure but also theft, fire, flood...

This is easy to do but this will require to erase the data I think. Either doing a factory default with the smallest disk only, then disabling x-raid2 and adding the other disks and choosing extend the volume, or by deleting the volume and recreating it.

You need to destroy the existing volume and convert to flexraid. xeltos outlined the procedure - you will need to restore all data, as the process is destructive.

Don't use RAID-0 to span multiple disks, as you will lose all data when one disk fails. Just jbod (with 4 separate volumes) instead.

Though you need a backup even with xraid, you need to be even more careful about maintaining a backup if you have no RAID protection at all. Also, I strongly recommend UPS for all NAS - no matter what the RAID mode is.

Thanks for the help guys, already have a ups so sorted on that side.