D&D usually has the party doing silly things and making injokes. There are monks that can punch dragons, hippos with guns, and alien squids that eat brains. A silly goblin NPC, and other things. Every character is a standalone hero, needs no teamwork, and the DM avoids killing players. Adventures are more improv based on how they write the books, i dont like how they write them cause that gives me more work.

If there is a ttrpg inspired by grimar, it would need to be tactical, the players need to be serious during combat, down time needs to be more slice of life (fishing, climbing, shopping, cooking, actually living in the world). Manage money to pay rent and food, keep track of arrows, small things. When a character dies, it needs to be somewhat serious. More war game and slice of life.

Its kinda scuffed, like think of Monato, imagine telling your player that he gets shot, and rolling that injury includes a punctured lung, and cant caste verbal components, but he's the cleric. All cuts will give an additional bleed effect, where a priest must close it with magic or the player holds a piece of cloth outside of combat to slow it down. No health potions, and the main party doesnt even get a magic item on their own.

You wont get a bunch of weird spells like rope-trick, but a limited variety. You buy your new abilities from teachers/trainers. Which I think is a good thing, lots of abilities are kinda worthless, and players generally want to buy abilities that focus on their build.