Doubt you need a surge protector the first trip out. Actually "surge" is the least of your worries. More likely low voltage, high voltage, bad ground and rarely reverse polarity. You need more than a $99 surge protector to get all this covered. Initially a simple volt meter and a three light outlet tester is fine.
Water pressure should be regulated to about 50 psi but a simple regulator is low cost an easy. Still may want to turn the water off if you will be away from the RV for an extended period. Water systems are built as flimsy as everything else.
Filter is mostly for taste. Potable water is safe to drink direct and a basic filter will not render non-potable water to be safe.
I have the first two but never a filter. OK to just get out once and get a feel for it.
