I just recently got into game - bought the ARR long time ago and stopped playing almost at start.
It was years ago, so i have no idea if it is Steam account or not - currently I launch start the game from launcher, without using steam client.

But - My account shows that it is Steam linked - does that mean that I need to buy all expansions etc from steam store or I can actually buy from square?
It would be quite disappointing if I buy Stormblood and Shadownbringers not from steam and get them removed after the fact.

So, my question is - am I stuck with Steam version and I should buy only Steam versions (since account is Steam-linked), or can I buy from a store I prefer?
Also - the free Heavensward key I got was from Square store, so that is confusing as well - if the versions will be delinked, will it mean I lose that one too?