The paid version doesn't have any extras, it's just a month ahead in development. As a patron, you also get the art preview each month. Some tiers get access to a short story I write in my spare time and vote for what happens in it, as you go higher in the tiers you get to vote for monthly polls to give me direction on some things, if you go higher up you get two votes for the polls and stuff like that. You might as well browse the Patreon page for all the details.
I don't like strong-arming my supporters for basic features. Support for the game allowed me to get more art and work on it full time, but people that can't support me should still be able to enjoy the game, hence the current setup.
The walkthrough must be updated, but it's freely available (linked in the game's folder as well). Maybe I should make the walkthrough a paid option though, since I hate working on it.
The game does have a combat system, but it's not the focus (I partially regret not taking the time to design a better system, but it's serviceable and since it's not the focus, it's probably for the best if I didn't go down that rabbit hole).