Trolls are a joke by the time you're up to the plains, and if you do an island base right, nothing will ever spawn on or around it.

Don't know what kind of tips you want. Are you looking at creating a spawn-free zone on your island? If so, use workbenches to initially neutralise the spawn on the island, since you can use their build radius indicator to see how frequently you'll need to place them to make the no-spawn zone overlap. Once you're done with that you can replace the workbenches with whatever other spawn-inhibiting structure you want.