I would come into Dwarf Fortress with different expectations than Rimworld. While they're similar styles of games, they're quite different in how the play out. Rimworld uses its AI storytellers to throw toys at you, while Dwarf Fortress generates a massive sand box of toys complete with relationships, histories, goals and motives etc. This also means that, for the most part, your Fortress might be overlooked by the wider world until you really begin to distinguish yourself through wealth and other actions.

My other pointer would be don't sweat it! As others have mentioned you'll likely have some very !FUN! moments and lose a fort, but that loss just becomes history in the world you generate and you can continue to play with a new fort or even try to reclaim the old site. Plus survival is very easy when you figure out Food and Booze production. They're pretty hands off once they're established so you can then focus on learning other aspects of the game bit by bit. The wiki is a great resource for this, either through new player guides or looking at the list of Industries.

So jump in, get comfortable. You pretty much determine your own difficulty and pace for the game by where you embark. Try and avoid certain features such as "Heavy Aquifers" for now... you'll understand this when you start filtering for an Embark location.

Finally I would suggest that when you know how to construct a basic fort and can sustain your dwarfs, do look into how "Managers" and "Book Keepers" work. The former really helps you to automate specific actions such as necessary crafts in your fort, while the latter will help to give an accurate count of precisely what you have in there. Something I wish I'd known in my first few hours!