I think that as an artist with very low sales, I would initially take the simplest route you can. You can do it yourself, or you can trust a distributer (aggregator) The important thing is to get your music onto Spotify, then the other platforms. I get far more from Spotify than the others. Most aggregators make life as simple for you as they can and they produce the registration codes as part of the deal. If you put them direct on the big platforms yourself, then you probably should also protect them, but doing this is boring, tricky to get right and not much fun.
I have accounts with
Distrokid - the biggest, (but known for deleting people's entire catalogue if you upset them)
They differ in terms of cost, complexity, territory and facilities. My music that generates money is mostly coming via songtradr, with smaller amounts from Ditto and Record Union. Distrokids was doing very well till they removed my music and froze my account. Songtradr I like because they are easy to navigate and get stuff up on the useful platforms. Some like covers, some don't and some hate classical music. Some charge you per release others a yearly fee for as much as you like. They all have good FAQ sections explaining what they do - and you will find one that suits that is simple. Money is ALWAYS three months at least behind. They also provide stats - so you find out which country and cities each title is played which is nice. Spotify sign up as an artist and iTunes/apple too is worth doing because then you also get stats direct from them.
The way copyright works is that as soon as your titles pop up on Spotify, iTunes, Apple Music, YouTube etc - the music is published and protection is there for all to see. If your music appears in a Spotify search with your details, you don't need to do anything because the evidence of ownership is there, and you exist, world wide.