For a start it is easier to carry a backpack than a bag but I guess you wont be planning on walking far.

To find places to stay go to google maps and type in Trang then zoom in on each island in turn. I just zoomed in on Koh Mook and see it is full of resorts as well as other places to stay. They even have a ting tong bar which would probably suit you.

Click on any one and a panel comes up on the left with info on the one you clicked on, most have reviews by people who have stayed there some have phone numbers and costs.

Do this with anywhere you want to go and make a shortlist. If they have a phone number call them, in Thai, and ask about things like costs, getting there, where to eat and anything else you want to know. By phoning you will also get an idea of attitude with the lady boss saying she likes the sound of one or the other.