If you only have a handful of TBs, you don't need RAID. RAID is stupid for home storage. There are 3 good reasons for RAID:
1. Speed
2. Uptime
3. Size
If you're having RAID for the sake of having RAID, you're doing it wrong. Having multiple disks actually increases the likelihood of failure of the system.
Let's say the failure rate is 10% for a single disk. For 2 disks, the chance of failure become 100% -(90%x90%) = 19%. That's nearly double the failure. For 3 disks it becomes 100%-(90%x90%x90%) or 27.1 It increase with each disk. If the failure rate is 0.01% or less, the math is easier to approximate and actually comes close to being a multiple of the number of disks. A RAID system with 10 disk has 10 times the failure rate. Yes you'll have the redundancy, so that you'll survive at least a single disk failure or 2, depending on your RAID level, but only if you know it failed and you replace the disk in time before the 2nd disk fails.
The reason RAID is used is because you need one of the 3 criteria I've listed. If you don't need any one of those 3 criteria, don't do RAID. RAID is used in a server system where there's supposed to be someone watching the system and getting alerted to replace the failed disk as soon as possible. For home use, it's much simpler and cheaper to use a single disk for storage, then copy it to a 2nd disk for backup regularly and having a 3rd disk for longer term backup.
As for software or hardware RAID, in real life situations, hardware RAID is more reliable, because you have dedicated hardware that does not rely on your OS being updated. By hardware RAID, I'm talking about dedicated stand alone units that operate on their own. EMC, NETAPP, etc.. for higher end stuff. Synology NAS for lower end; it's the only lower end one that patches regularly, then other don't.
RAID cards are not as reliable as real hardware RAID and you may have to reboot your system to access the RAID configs, if you buy cheap cards. Newer cards have drivers that can be operated and controlled from within your system. These are cheaper than the dedicated Hardware RAIDs and used by smaller companies that want cheaper systems and really are partially software RAID.
Software RAID are for people being cheap and wanting RAID for home, not understanding the 3 criteria for RAID. RAID is not backup.
RAID 5 is obsolete for any spinning disks over 1TB. Even if you replace the disk immediately, the probability of a 2nd disk failure is too great, and will likely fail before the rebuild completes. It, may, or it may not, but the chance is high. You must use RAID 6. The disks are purchased at the same time and most people bought them from a single source meaning the disks were likely from the same batch, with the same manufacturing characteristics. You can still use RAID 5 with slightly larger SSDs, but once the rebuild time increase beyond a few hours, you're taking chances. During a rebuilt all the aging disks are being heavily taxed, increasing the chance of failure.
If you are using less than 18TB, you can buy single disks that hold that much data. You don't need RAID.
