Hey there,
yes you get full access to the current full version including the possibility to unlock all decks etc. You can download that version and play forever but you won't get new content for it.
The higher tier gives a Itch.io full Version on top, which will be updated but not regularly, so you could come back in a year or when the Game got all remaining updates and have new content.
On top, the higher tiers get the newest version a bit sooner and get bonus Arcane Dust to unlock decks etc. faster. The game is the same though.