that score multiplier dont affect your rings/score in the race, but it does affect stage grades (for rewards in the game, very small tho) and how fast you climb the rank leaderboards.

As f2p, best you can get is ~1800% ish, dolphins is ~2400%, whales is ~4500%

its pretty much a casual endless mobile game, just 15 mins to clear the dailies, play until clear all the current rewards. Great time killer when travelling (its been available here since last year)

There is Emerald League ranking and squad ranking where placing high matters a lot

nope, well atleast not during the race. Only advantage they give is the "score multiplier" to clear daily/weekly objectives a bit faster

The skins are expensive but they dont give any advantage or extra rings during the game like some reviews claim, so no need to worry on that front