1)Which leagues do you find the most predictable in terms of match outcomes?
2)And which leagues are the most unpredictable, where you can’t always rely on teams' form or stats?
It actually depends on what exactly you are looking for. If you want a game that's far easier compared to some others to predict, I'll Go with English leagues and German leagues. The only thing is some times the odds can be very small which compensates for the high chances of the game playing out.
However, on the other hand if you are looking for bigger odds kinda like a jackpot other leagues that are not too popular are a better choice. The only thing is the chances of winning are way thinner.