There are 3 different "account types" which you can use to play Guild Wars 2. The original Arenanet, Steam, or Epic.
Just like Apple vs Google, or Windows vs Mac, there are a lot of very strong opinions out there about whether you should run Guild Wars 2 through Steam or Arenanet. There are advantages to both and it's ultimately up to you to decide which path you wish to take.
In my case, Steam wasn't even an option when I started playing GW2 and I've stuck with my Arenanet account since then. The option was offered when GW2 first came out on Steam to transfer your account and not lose anything but I opted to just leave things as they were. I don't believe that option is even available anymore.
I also believe that Epic now has a GW2 launcher and that you can create your account through Epic now. I haven't delved into that yet so am not familiar with what the differences would be.
You can start your account via either one but the difference is that the codes for expansions, gems, etc., must be bought through the platform you created your account on. If you go through Steam or Epic (I believe), this means that some of the giveaways from streamers won't work for you because they're Arenanet codes, not Steams codes. This isn't true for all streamers though so make sure you ask the streamer.
If you start your account through Arenanet then you can still play through Steam BUT you'll need to put a "soft switch" in the launch options for GW2 in Steam
If you want to sign in with your Arena account, right click on Guild Wars 2 in your steam library and select Properties. Then paste "-provider Portal" (without the quotes) into the "Launch Options" box.
If you do that then you will login through the Arenanet portal and have access to your account just as if you logged in through Windows. That will allow you to use the Steam controller functions with GW2 even if you have an Arenanet account instead of a Steam account, if you wish to play with a controller rather than keyboard & mouse.
This will also allow you to play GW2 in Linux with the Steam Proton functionality. Steam has done a good job of making Steam games available to play in various Linux distros without having to have a lot of coding knowledge or terminal experience.
I won't go into it here because it's something you'll need to look up depending on which distro of Linux you're running. There are plenty of guides on the internet though so you shouldn't have any problems finding the into.
In my case, I have installed Steam, and GW2, on to my Ubuntu system and haven't had any problems so far. I'm able to access my Arenanet account and all my characters, history, etc so it can be done.
Which account method you choose is entirely up to you... just have fun playing either way!
Good luck and have fun!