When you're turning you will be able to see the boat in your mirrors.
If you've towed it before then you know how wide to swing turns, no different with the camper on.
If you're worried it will still be back there after running down the highway, don't be. Have you lost a trailer before??
As far as backing up goes, either you know how to back a trailer or need to learn/practice. You could always mount some flags off the sides of the back of the trailer so you have a visual aid in your mirrors.
Last but not least, use a spotter when backing up blind. Should be standard practice anyway.
Or get a new back up camera. It's a convenient feature but it can be a band aid for lack of skill just like ABS, sway control, tpms, parking assist, etc.
Most of these new tech features are just turning people into bad drivers.
There's no substitute for learning a skill or realizing your limitations!