Anyone pulled over by CHP?

You'd have a better chance of getting pulled over for speeding. My FIL was pulling his 5er and was doing 65 down a slight grade. Got a ticket for $400

If hypothetically; I were to get pulled over by CHP to verify my trailer weight, what number would they check? The max GVWR?

You will have as much of a chance of CHP or any LEO anywhere stopping a RV "just for a weight check" as you will have a rich uncle leave you a million bucks.
CHP or DOT doesn't use a vehicle GVWR for how much load the truck can carry. What they do check is tire and axle ratings.
This from a RV.net member (I think) who had the same question for CHP.
Its long and I snipped for length;

****
The California Vehicle Code (CVC) does not contain a law that
specifically limits the amount of weight a vehicle may tow based on the
towing vehicle GVWR or GCWR. There are, however, laws that limit the
amount a vehicle may tow based on other criteria.

Title 13 California Code of Regulations prohibits
the loading of tires above the maximum load rating marked on the tire,
or if unmarked the maximum load rating as specified in the applicable
Federal Motor Vehicle Safety Standard, or in a publication furnished to
the public by the tire manufacturer. This would most likely happen in
the case of a pickup truck towing a large fifth wheel travel trailer, as
those types of trailers tend to transfer a larger portion of their
weight to the last axle of the towing unit causing that axle to exceed
the tire load limits.*****
I trust this has adequately answered your questions. Should you desire
any further information, please contact Officer Ron Leimer, of my staff,
at (916) 445-1865. Sincerely,
S. B. DOWLING, Captain
Commander
Commercial Vehicle Section" *****

So there you have it from the horses mouth. Just stay under the trucks axle/tire load ratings for how much load the truck your truck is carrying.
If I was concerned with what any state DOT says about overloading I would check with them myself.

I'd be more concerned that truck can safely handle larger/heavier trailer vs CHP pulling over to weigh.

Have you been across set of scales with current truck a;; camp ready to know what you have in regards to GVWR, AWRs and payload availability?

Nothing worst then to buy a trailer and THEN find out it is overweight....

Probably the only time it might come into question would be in case of an accident. I remember years ago a fella I worked for was leaving a bar one night and drove his truck off the road. Next morning when he went to pull it out of the ditch he was ticketed for defective tires. Yea, they were bald, but that was not the cause.