First, there is no absolute security. Given the time and the interest every game's resources can and will be extracted somehow.
Second, your resources will automatically be protected (it's your work) and to be sure, put them under a license.
With that in mind it mostly just becomes a question of trade offs. How much time to do want to invest obfuscating your resources and how probable is it, that anyone is even interested in obtaining the resources?
For your small games, it's probably not worth adding the extra layer.
If you still want to do it, there are many ways.
One of the simplest would be to use physfs or similar, which is basically just an archive and lets you stream data from it. If it's just an archive, then many programs will be able to extract it.
Another option would be to create your own binary format that you know how to read from and write to. Without the source code, it can take quite a while to reverse engineer how the format works, but it's also a bit harder for you to maintain it.
With both versions you could try an obfuscate the data you're saving or reading, that way people not only would have to figure out the format or unpack the data, but they'd also have to reverse engineer the obfuscation.
In the end, without proper hiding mechanics in your application, good reverse engineers will just be able to run your application and grab the data once it's been decoded.
Personally, I don't think it's worth spending much or any time on. The main reason I'd use something like PhysicsFS would be to have all resources in one archive as oppose to everything being cluttered in multiple directories.
