Hello,
As Flying Blue Platinum you get to select a standard seat on Air Mauritius for free, Comforto+ on GOL, preferred seats on DELTA (and allegedly Delta Comfort+® seats, if Lynette from MSP is in a good mood), comfort seats on Kenyan, and obviously all available seats on Air France and on KLM (including economy comfort).
On other SkyTeam partners it’s up to availability, the agent’s mood and most of the time, a fee.
If the flight is provided by a partner airline with an Air France flight number you may check in an additional baggage item at no extra charge on CERTAIN partners, but that’s it.
Seat benefits apply to AF/KL-marketed AF/KL-operated.
But not on Air Baltic.
All seats offer the same legroom onboard except emergency exit rows. Hopefully, you’ll still enjoy your flight. Air Baltic is great.