I'd say that removable floor materials are a must to permit maintenance access, as stated. Also, for cleaning and moisture remediation.
I painted my floor, then applied strips of Dynamat between the ribs. Then, laid down a foil-backed jute layer. I think I got this from quiet ride. On the top is a rubber mat I got online from Farm n' Fleet - bought bulk material and cut to fit. The rubber is chicom and not that great quality, but it's held up ok for about 10 years of regular use.
I have driven the truck with and without the jute under the rubber mat, and the jute definitely makes a difference in sound. It takes the higher frequency road noise out of the cab.
I think this is the same mat that @Merle Coggins used....
https://www.farmandfleet.com/products/516709-flexgard-48-x-72-x-1-4-multi-use-utility-mat-100-rubber.html