Surge protector is OK. But you really could use, IMO is a EMS (Electrical Management System)...mine is from Progressive Industries. I camped for over 20 years without one...then one day a nearby lightening strike hit and fried my fridge ($1300 to replace) and damaged my INverter (fixed)....the $300 or so for a EMS is alot cheaper than $1300,plus $180 for an on-site tech to get the INverter straightened out. That's when I bought the EMS system.
Water pressure regulator....my experience has been that the campground itself will tell you water pressure is unusually high so they reccommend one. Buy it there. Couple bucks...then you have it forever.
Water filter. Never had one. traveled from NJ to California and back four times....sometimes water tastes different, but never got sick or had any problems. That doesn't mean i never carry my own water (couple gallons in milk containers) just 'cause y'never know.
g'luck in your travels!
