At most Connecticut state parks, the campsites are huge. Not a lot of hookups, though - you are mostly "dry camping", no water supply or electric hookup... you need to use your camper's fresh water tank and battery power supply. Or you can get a portable generator. Or... your Class C may come with an onboard generator.
I have never heard of 21-22 foot length restrictions anywhere in Connecticut. Were you talking to a person with experience with RV type camping? He or she may just be mistaking what they overheard, or more may have been talking about a specific campsite somewhere.
You will be fine with a 25 foot Class C. You will find all sorts of campgrounds in CT, both state parks and private campgrounds. You will be surprised at all the places to explore in CT that you didn't know about.
Then you will expand your camping to surrounding states and be amazed at all that New England has to explore. Upstate New York, Maine, etc - countless campgrounds and things to discover.
Then you will head down the east coast, and may end up at Fort Wilderness in Disney World.
Then you will look westward and realize you want to retire early to try to see EVERYTHING!
Have fun!
_________________________________________________________
2021 F150 2.7
2004 21' Forest River Surveyor