This may be redundant but I would like to know

I don't know about Federal or elsewhere, but pretty sure in California you have to have a CDL if your trailer gvwr is over 10k.

I got pulled over in a company F350 with a single car trailer one time for speeding, and the cop expressed surprise when he got my license, because he thought he was going to get an out-of-class ticket too just based on looking at the trailer.

It was the first time I had driven that truck, and I had not yet done a speedo check on it. (This was before smart phones and GPS lol), and so I asked him to pace me and flash his lights when we got to 55, and he didn't write me for speeding.
(it was way off...)

 

Ryan,
Glad to see you are still giving it a go and asking questions. Simple answer, CDL requirements are based on the manufacturer declared gross vehicle weight rating. So even with the trailer over 10,001 pounds as long as the gross weight rating of the truck and trailer together do not add up to more than 26,001 pounds you will not need a CDL. As soon as those two ratings or the actual scale weight when inspected exceed 26,001 pounds you jump from no CDL needed right into a class A. These are the actual ratings as on the door plate and tongue plate of the vehicles, and don't confuse the trucks gross combination weight rating, that is simply the maximum combination weight it can tow but you only need to be licensed for the actual combination weight as presented at the side of the road when being inspected by DOT.

These are Federal rules, all the states have to abide by them, that was settled many years ago when New York had the class D non-cdl that was good only up to 18,000 pounds and they were ticketing people for driving rental trucks and such.

 

The actual weight of the vehicle and trailer does not matter for CDL, it is the Combined of the truck and trailer GVWR that counts. Add the Trailer GVWR to the Truck GVWR that determines CDL requirements. So your tow vehicle has to have a GVWR of 12,000 or less with a 14k GVWR trailer if you want to avoid CDL. After that you need to calculate your axle weight which will vary depending on how you load your trailer. For example if you put the heavy car closer to the truck more weight from the trailer will end up on the truck. You will need to go to a CAT scale to figure this stuff out.

 

States have to abide by Federal rules, but they can be more strict.

And California is! (on a lot of things...)

If in California you tow a commercial trailer over 10,001 pounds gvwr, you have to have Class A license, except for some specifics like a farmer hauling his own livestock.
I wouldn't be surprised if other states have similar laws, but I know CA does.

https://www.dmv.ca.gov/portal/dmv/detail/pubs/cdl_htm/lic_chart

 

It looks like Massachusetts requires Class A for trailers over 10k, just like CA, and that North Carolina doesn’t go by gvwr, but by actual weight (don't remember what the cut offs were), and some other states use the FMCSA layout.

On the FMCSA site where they give the Federal rules, they have this disclaimer at the bottom :

"States may have a more restrictive category for a class of license, or have additional codes for endorsements or restrictions on CDLs that are not mentioned in the Federal regulations, as long as these items are fully explained on the license document."

Basically the CDL system is to ensure a consistent level of training across all the states, and prevent people from holding several driver's licenses to run multiple sets of books, but the actual class break is variable.

 

What you are missing is you do not add the weight of the cars to the gross weight rating, the gross weight rating is the total of what the truck, trailer, and cargo can weigh not what they actually weigh empty. So your truck has a gross of 10k but really only weight about 8k and the trailer has a gross of 14k but really only weights about 7k leaving you about 9,000 pounds of cars or other cargo to carry. So the only time you will have to worry about needing a class A is if you are overweight for the combination and if you are you will have other problems anyhow. To be sure you will have enough cargo capacity get the actual empty weight of the truck and trailer and subtract that from gross weight ratings and that will be your carrying capacity.

 

As Brian said, you have 2 numbers.

The GVWR - Gross Vehicle Weight RATING, which is the maximum total weight the vehicle is allowed to put on the ground (what the scale would say).

Then you have the Tare or Unladen weight, which is the empty weight of the vehicle or trailer.

The difference between these numbers is your Net or Cargo weight capacity.

So if your truck weighs 8k (the Unladen or Tare weight), and the GVWR is 10k, that means you have 2k of Net or Cargo capacity. You can haul 1 ton without overloading it legally.
Now, that 1 ton can be firewood in the bed of the truck, or tongue weight of a gooseneck trailer, as long as the 2 axles of the truck (the GVW) don't exceed the GVWR (the Rating for max GVW) of 10k or whatever it is.

You also have to see what the actual axle and tire weight ratings are.
My F350 has a GVWR of 9900, a front axle GVWR of 5200, a rear axle GVWR of 6830, and the tires are rated for 3,415 pounds each.
So my tires exactly match my rear axle rating (and I often see tires, especially on trailers, that are too light duty to allow a fully loaded vehicle rating, and they do check this, so so should you! Lol)

So you have to find out what your gross and axle ratings are (the sticker on the door post, or on the trailer), then weigh the truck and trailer empty (though make sure you have full fuel tanks, and all the tools and luggage you would normally carry with you.) this gives you your Unladen weight.
Now you subtract that from your GVWR, actually from your GCWR (Gross Combined Weight Rating, the combination of your truck and trailer's GVWR'S. So say it is 24,000k, that is the GCWR), and you have the maximum cargo weight you can carry.

Once you get to load, you still have to figure out how to load it to not exceed the axle or vehicle weight ratings, so in the example, not more than 2k on the truck, and the hitch has to be positioned correctly to distribute that weight properly between the axles.

This all sounds complicated, but once you get a load on it, drive on a scale, and check how much is on each axle, and then look to see how you have the cars positioned. You will get the hang of where to put them to match your rig, it is just figuring out a new set up that takes a bit of work, but it is just playing with the numbers until they match.

As far as cdl and legality, some states only look at the GCWR (truck and trailer combined max Rating), some base it on the Trailer Max weight rating (the GVWR) (California and Massachusetts at least, probably others), and some base it on the actual scale weight. (North Carolina?)

So since your trailer is over 10k GVWR, you will need a Class A in at least some states.
If you don't want to get it yet, decide what states you want to run in, and check their license class rules, and just stick in the states that allow you to be Class C as long as you stay below 26k combined GVWR.