id say meta knight is definitely the easiest, tho is upB recovery isnt that standard. but fast easy attacks and multiple jumps helps. maybe samus also. someone earlier suggested peach and sonic... i wouldnt call them beginner friendly at all. sonic is the fastest and can be quite tough to control, and to get good with him, most of his game are grabs and precise edgeugarding, and peach relies a lot on smart projectile use and float cancelling.
subspace will help u get familiar overall, even if the characters are slightly tweaked (they barely are, possibly just a lil faster running speed to make it seem like a better platformer). but yea go for like meta knight, samus, kirby, mario.