I'm not a gamer (is that unusual around here?)
Not necessarily. Just because some people tend to sometimes play games, I would not call them gamers. Everyone gets their fair share of entertainment in one way or another. Some just like spending time in-game via Steam.
but it's nice to see that steam is accepting bitcoin and that you had a relatively problem-free experience.
I don't think that some realize just how huge Steam is.
So you might be interested in Piranha Bytes games, they created series like Gothic and Risen.
I'll look into it. The others have been beaten long ago. Are these games listed on Steam?
Call me paranoid but I don't fully trust sites like g2a or instant gaming. here's probably low risk to get scammed, but I think it's better to buy it from the real deal (the steam platform) and have a peace of mind that the key delivered is yours and only yours and has never been owned by anyone else.
That does seem a bit paranoid. If the key is used by you, it usually can't be used by anyone else.
I'm just going to comment on your last point, the issue I've always had with G2A is not that the key is being used by someone else, but rather that the key has already been used. If I remember correctly, G2A is like a sort of Amazon for games, and thus people sell their own goods and it is just insured that you'll get your product by the site. There have been some issues with used keys being sold to people (who can't tell if it has been or hasn't been used) and then they get scammed out of their money, unless they bought G2A shield.
Once you do redeem the key, though, it is yours and no-one else can take it in any way, unless they take your whole account.