Best sealants and adhesives for exterior and interior of TAB

Pictures always help.
The consensus seems to be to avoid silicon.
For hanging stuff on the wood, plastic, or laminate surfaces I use 3M Command Strips.  I think many other Tabbers also use them.  I have heard that attaching things to the "wallpaper" type coverings has caused the wallpaper to peel away from the substrate.

If you are referring to the trim pieces that are on the roof edge where it meets the wall, that is cosmetic only. Don’t try to seal it to the roof.

The Command strips seem to work well on smooth non-porous surfaces.  I don't know how well they would hold up on an exterior surface exposed to weather.

I have had a Command Adhesive hook on the outside of my T@B for 13 years. It stays on all the time. It is my rain jacket hook, so I don't bring wet raingear inside. I also used to have small command hooks along the edge under my keder rail for light strings. They never moved either. When I did want to remove them, the strips left a residue that I had to remove very carefully with a razor blade.

So yes Command strips work well on the outside.

@HAWAIIANTAB... and anyone else who might be reading 🙂. Here's how I think about the importance of NOT applying caulk to the exterior plastic trim on our campers.

One reason the plastic exterior trim pieces are cracking is because they are designed to be tightly screwed to the trailer. As a result, the individual pieces are not allowed to expand and contract as the temperature changes which is  causing pressure... to the point of fracturing. It seems logical that applying caulk between the individual pieces to 'seal' them is going to increase the odds they will crack. Similar to what would happen to vinyl house siding if it were tightly nailed. Instead, it's designed to 'float' on the it's slotted nailing holes to allow for expansion and contraction. But, of course, it isn't possible to attach our camper's trim in this way. Nevertheless, applying caulk would further restrict what little expansion the trim is permitted.

Another consequence of tightly screwing those trim pieces is that they are going to be constantly flexing with the trailer as it travels down the road. This adds stress to the trim's fragile plastic construction. Applying caulk between the plastic trim and the camper body to 'seal' them is also going to more securely attach them and exaggerate the flexing.

Avoid applying caulk to your camper's plastic trim.

BTW I used solar outdoor lights movement and night activated. S cured with 3m heavy duty Velcro. Forgot to turn it off while traveling. Everytime I passed something the light came on until the battery died. Very interesting to other tlroad users I'm sure.