It has been a long time since I have done the experiment , but a few tips.
1. Fleet speed only as fast as the slowest ship in the fleet
2. Need to have max crew for max speed.
3. Cotton sails and double hammocks are the 2 upgrades that affect speed.
It is best to simply experiment.
Create a fleet with a single ship, hawker for example, max crew, hammocks and sails to 10. Then look at the travel calculator on the fleet screen to see travel times to each port.
Next try the cutter, sloop.... etc.
Once you know the travel time to a port, and the cargo limits, you can calculate trade profits.
This is just the basics to get you going. There is a lot more things to consider when setting up trade fleets, but learn the basics first.
Cheers