Texas requires a CDL if it is a commercial vehicle and meets Class A or B requirements with a few exceptions. Commercial farm vehicles not going over 150 miles away from the farm and firefighting vehicles are two but you must have the appropriate non-CDL class license for the vehicle. I had a Class A non-CDL to drive firetrucks. Our Freightliner FL70 ambulance had a GVWR of 28,000# and required a Class B non-CDL or Class B CDL to drive it.
Texas requires a Class B non-CDL to drive a non-commercial single vehicle over 26,001# GVWR towing a trailer not exceeding 10,000# or a farm trailer not exceeding 20,000#, which includes RVs. My parents pusher motorhome required a Class B non-CDL. A non-commercial combination of vehicles exceeding 26,001# with the towed vehicle exceeding 10,000# requires a Class A non-CDL.
Depending on the year and axles the Freightliner M2 Sportchassis could have a GVWR from 18,000# up to 54,000#, although most are around 20,000# for the soft ride. With most GN trailers you will be in a Class A license situation in Texas, either a non-CDL or CDL depending on if the vehicle is used for non-commercial or commercial work.