More drives is always better. But you need to understand how you are making it better.
en.wikipedia.org/wiki/Standard_RAID_levels is a good breakdown of the different RAID levels. Those are slightly different depending on if you are doing “real”/hardware RAID or software raid (e.g. ZFS) but the principle holds true and the rest is just googling the translation (for example, Unraid is effectively RAID4 with some extra magic to better support mismatched drive sizes)
That actually IS an important thing to understand early on. Because, depending on the RAID model you use, it might not be as easy as adding another drive. Have three 8 TB and want to add a 10? That last 2 TB won’t be used until EVERY drive has at least 10 TB. There are ways to set this up in ZFS and Ceph and the like but it can be a headache.
And the issue isn’t the cloudflare tunnel. The issue is that you would have a publicly accessible service running on your network. If you use the cloudflare access control thing (login page before you can access the site) you mitigate a lot of that (while making it obnoxious for anything that uses an app…) but are still at the mercy of cloudflare.
And understand that these are all very popular tools for a reason. So they are also things hackers REALLY care about getting access to. Just look up all the MANY MANY MANY ransomware attacks that QNAP had (and the hilarity of QNAP silently re-enabling online services with firmware updates…). Because using a botnet to just scan a list of domains and subdomains is pretty trivial and more than pays for itself after one person pays the ransom.
As for paying for that? I would NEVER pay for nextcloud. It is fairly shit software that is overkill for what people use it for (file syncing and document server) and dogshit for what it pretends to be (google docs+drive). If I am going that route, I’ll just use Google Docs or might even check out the Proton Docs I pay for alongside my email and VPN.
But for something self hosted where the only data that matters is backed up to a completely different storage setup? I still don’t like it being “exposed” but it is REALLY nice to have a working shopping list and the like when I head to the store.