I would definitely not recommend pokerstars Spin & GO. Back in the days I played there a lot and most of the time multiplier was x1 so it means that you will win the same amount that you spent for buy-in. The highest multiplier was x5.
I believe that in unibet´s hexapros i have managed to get 25x multiplier twice on 2€ buy-in. And in 10€ one once got 10x multiplier ...
In Bet365 biggest multiplier i have seen is probably 5x on 5€ ...
And in stars - there i have never got any decent multipliers lol ...
i have to also give points for Unibet´s HexaPro....
5x r quite common...
I have had on 5€ lvl....10x a lot of times....best was 3times a row...shipped all of them...
fields r a lot softer then Stars...
do not play on Party so cant tell about them...