Plinko offers different multipliers for different risk levels and number of rows. The odds thus change according to the multiplier on the Plinko board.
The house edge is set at ~4% for Low, Medium and Hisk Risk level while Extreme mode has house edge set at ~8%.
As an example, here are the odds for 8 rows Plinko, all risk levels for over 1,000,000 iterations($1 bet):
Note: Odds used for calculation above are rounded up to 4 digits only. You may find actual odds by hovering over any multiplier on the game page.