20$ is quite fair for what you receive. The VPS offered by DO and Linode are hosted on high quality servers which makes a huge difference when it comes to things like encryption and possibly plex transcoding (in case you are using this). Quite often when you see offers around 5-10$ for the same or even better specs you end up with a shared Intel Atom and really poor performance regarding network and hard drive. Trust me, you won’t be happy.
You can actually create additional volumes if you choose DO’s datacenter in New York or Frankfurt (not quite sure about the other one in the US) in case you run out of space.
If you need more you are better off with a dedicated server.
I use time4vps.eu. 4TB hdd, 4GB Ram, 32TB bandwidth for 14Euros/month. Does the job pretty well. But, then it does not fly like a standalone system. I have streamed plex, and also done some heavy downloading. The vps does the job okay.
I am using EthernetServers.com Currently they have an offer for 4 Cores, 4TB of data, 4GB of ram for $30/year. Check them out to see if you like them. They also have monthly plan. I am currently using one of the $30/year plans and one of the vEth plans with 8 cores and 4 TB of bandwidth. I use them for plex, rclone, and all my other download utilities.
I’m using a combo actually. My VPS is in Russia with a “DMCA friendly” provider (vps9.net) for torrenting as well. And then I spent $10/mo for 1tb of storage with Google drive and store everything encrypted on there via rclone/plexdrive. Works super well. Vps9 have pretty good prices too. Storage on there is expensive though so you’re gonna need some sort of external storage like gdrive.