Hey Layton,
I’ve also been toying with the idea of the M rack on my mega cab but don’t want/need a light bar. So I’ve been putting a parts list together from ez awn and 8020.net using their aluminum extrusions (same crap on the m rack). In terms of weight capacity, a Jeep Wrangler has a fiberglass hard top and it has a dynamic (driving) capacity of 150lbs for reference. Static load capacity would mean at rest.
I do not think you’d have any issues at all running the m rack which is super light weight and a kayak or two.