I have a 20' CargoMate Blazer that I use to haul my Corvette to events. It's just big enough for the car and a small Craftsman chest and an aluminum storage rack. While there is plenty of room in the trailer when the car isn't in there, it is crowded with the car loaded and tied down.
One thing to consider is the loaded weight. My trailer has a total weight capacity of 7000lbs. While that seems a lot, the trailer weighs just under 3000lbs. The two axles are rated for 3500 lbs each. The car weighs about 3300 and I figure the tools, race tires, and equipment weigh about 500 lbs.
I tow the trailer with an '08 Silverado 4x4 with the 6.0L motor and the max towing capacity is right around 9000lbs. A 24' trailer would be an improvement ig help but I would need a bigger truck.
A small generator can work but it should go on the tow vehicle. IMHO, you don't want to have a generator running that is close to the trailer. It's easy for exhaust gasses to float around and get into the trailer. Wiring the trailer for 120v is not that hard as long as the trailer in not pre-finished inside.