Yes and yes. Small harvesters have a cargo limit of 500 per trip. Harvesters have 1500, cargo ships have a hold of 3000 if I recall and not sure what Freighters hold, but you can see what all ships and orbitals have in ATK/DEF and Cargo Limit by clicking on the More info next to the ship in the Factory Page. Trade works a little differently, but it is all based on your cargo limit and distance from Trade Planet to Destination Planet. There are some very good threads on the forum about trade and how it works. The search function is now working properly, so just type in trade and feast your eyes on all the treads.