Vinyl is vinyl and it will shrink and expand with temp. changes regardless. Sheet vinyl can crack/tear in cold temps. at stress points like floor vents for ex. Sheet flooring as stapled all around the perimeter and everything is built on top of it and can't move much at all in comparison to a free-floating laminate plank floor.
One very important key to laminate flooring is providing an adequate expansion gap all around the perimeter and at places like table flanges, toilet, etc. where it can get hung up and pull apart. Use the click & lock type. Use a small baseboard material around the perimeter as needed to hide the expansion joint. Don't goop the exp. joint with silicon as one owner did.
I installed laminate plank laminate in a previous Coachmen TT 5 years ago and used a brand made from ABS. I don't know how the coefficient of thermal expansion compares to vinyl. My BIL bought the TT from us and lives in a much colder climate and reports that it has been perfectly fine for several years now. ABS is very rigid tho. and harder to cut and not sure if it's available anymore.
Three winters ago it got abnormally cold for an extended period and there were many reports of RV owners getting cracked sheet flooring. It's hard to tell what the summers and winters will be like nowadays and depending on where you are, you may want to provide for the worst case shrinkage.
Regarding the toilet, be careful about the increase in distance from underside of toilet to the flange. RV toilets use a foam gasket and it may not seal with the increased gap. Some have used an ordinary wax gasket. If you can, shim the flange up with something to maintain the same spacing. Always replace the gasket if you lift the toilet. Water leakage is not good for an RV...
Gil & Deb & Dougal the Springer Spaniel