Thx for answer!

Any support questions will be a mess if you have different account names and you might not be able to let steam auto generate the account if you really need a different name.

I already have Factorio account o I need just to link it with my Steam, I know. But what about support ...

I gonna get license in Steam soon. If I link my account on site with Steam account did I get possibility to download Factorio directly from website (just dislike like Steam but for my region it gives me something around 65% off)? And what about difference in Steam username and Factorio.com username ...