Having a hot spare vs using all your disks for home/SMB

I recently got a 4-bay NAS. It’s an older model that my work upgraded from, so I put it to use at home (Netgear Readynas RN-314). I installed double the RAM on it to 4GB and it’s perfectly fine for basic storage for me. I’ve started making YouTube videos and thought having a larger storage with some redundancy was worth it as it quickly outgrew my 1TB laptop.

I’ve got 4x 3TB drives in it as RAID 5. One disk is brand new as it had a failed one in it when I got it but the other 3 are well used. If having the extra capacity of all drives in use isn’t necessary for me yet, am I better off changing the pool so it’s 3 disks and leave one disk as a hot spare or does it not really make a difference? I know, RAID is NOT A BACKUP, but I’m not in a position financially to have multi-terabyte backups, so want to maximize its resilience. Or maybe I’d be better off as two sets of RAID 0 pairs that make a RAID 1?

Also on that note, for a home user/beginner with a single NAS, are there any inexpensive backup methods to consider? The only thing I can think of without spending a bunch of money is an external HDD and just making an exact copy of the data occasionally, which is better than nothing but inconvenient (and will get to be a very lengthy process as data grows). Or software you recommend to-do differential backups to a separate HDD?

If you have reasonable NAS access keep the spare drive “cold”. Hot sparing is a compromise in several ways.