If the Belle Poule is teak/white oak you are going to have some troubles penetrating the hull, but it's doable. Medium cannons are better for medium ranges because they have more dps and more punch, but less penetration than longs.
Depower the sails, it helps alot. And if you are sailing the surprise or trinco depowering sometimes is not enough, you need to depower and trim sails to neutral wind force.
Trinco and Endy used to be the best on their class (Essex could be too but lacks chasers). Now with the introduction of Hercules and Le Requin, we don't know anymore.
Bots don't sell carronades, carronades are crafted by players only. Must be them to put contracts in the port markets.
In my opinion it's a weak hull for a trinco, have speed but can't stand much combat. Better go for teak/teak or teak/white oak.
Use all perk slots, if you are using less you are in disadvantage to other players out there. You can change when you want, you must have Reset Perks Permit. For me Double Charge is optional and Double Shot is very important.