Well I still will be learning new things as I never done any 2D projects, I am just somewhat familiar how Unity works that all. And personally, I am more interested in the dev stuff than art and design. So I wanna do it myself from scratch. Also I feel like Unity gives me more freedom over what I wanna do in and with the game. I also don't know how much time I will have for this jam due to personal reasons, which is another reason why I will stay with unity and not currently learn RPGM as a new engine.
Although if i will have time when the next jam appears, I might try RPGM if it will fit my game.