Your operators manual is the best source of information for such a question, with regards to towing.
When I started, I pulled my camper very similar to yours with a 6 cyl station wagon. I set the cruise for 55-60 and shifted the trans into "sport" mode, which the operator manual pointed out delivers more low end torque and was recommended for "spirited" driving, towing and hilly terrain.
Since your Tacoma has the towing package and towing button, hit it and let the computer worry about your transmission... no need to turn off the overdrive unless instructed by your operators manual.