I get the benefits of IGH are many, straight wide chain, stronger wheel (usually), nothing hanging down, simple adjustment.

The negatives outweigh that---for me. Weight, drag in the system, pain changing flat, narrower range than 11/32, initial cost, inability to get fixed if broken internals. I love the easily repaired nature of a derailleur bike.

Loaded touring pulling a trailer, since that is what he already has that is what I would stick with.

Back onto the initial questions. Go very light and look closely at the gravel road pack to adapt them to your use.

Rick