Hose question........

we expect to camp in parks with full connections.

Any thought to a water pressure regulator?

Good insurance, but definitely not guaranteed if you leave water spikot on all the time. Personally myself I dont and just fill tanks when I need to.

Very rare to need more than 25' fresh water hose or more than 20' sewer hose.
Worst case pick up what you need at the camp store. Carrying tons of extra stuff just in case will bury you in junk.

I carry one 10' water hose (spigot to water filter) and two 25' water hoses (to reach the trailer). I carry one 15' sewer hose. If that is not enough, I break camp when needed and go dump.

For the tank flush, my TT has a backflow preventer built in. I bought a 6' water hose and two more backflow preventers. I put one backflow preventer on each end of the 6' water hose. I feel safe using the 6' water hose attached to my drinking water hose as a flush. Three backflow preventers would all have to fail to contaminate it. (Those who demand a dedicated hose are still hooking their dedicated hose to the spigot where they get fresh water.)

I use a water filter whenever we fill the fresh water tank or use shore water because at one campsite in Florida (in 2009), I got sand in my water system and never got it out again (sold that RV in 2017).

For fresh water from site spigot to camper we carry a 10ft. and 20ft. Use the 10ft. most of the time. For sewer hoses we carry a 10ft. and a 20ft. with a coupler to combine the 2 together if need be. Again, we use the 10 ft. mostly. Also, keep in mind that these hoses particularly sewer hoses can take up a lot of storage space.

Do a search on outfitting a newly purchased rv

We use 2x25' water hoses - food grade not garden hoses! Sewer hoses , one 15' sewerand , one 10' and one 5'........ we always seem to need a few more inches. Yes, you should use a different hose for the rinse connection on the sewer tank.Enjoy the adventure!

Plan on your own flush hose. Make sure it is a different color than the fresh water hose.

Why connect to city water? Fill your fresh water tank and use that. Much less chance of a water line problem.

Black tank flushes are nice but if you fill your black with water before dumping, you don’t need to flush very often.

Fresh water - a minimum of 50 feet. You should do 2 - 25 footers. Just get a regular garden hose for the black tank flush, although Camco has a pretty orange one for that.

Rhino has a 20 foot kit that is 2 - 10 footers and the ends. Standard Rhino cheaped out when Camco came out with Rhino Extreme.

Going to be different for every park.

Start with maybe 2x 25ft fresh hoses and a 10ft Rhino sewer hose with the 10-15 ft extension hose kit (comes with the coupler). Can't comment on a flush connection, no experience there.

How's it for Electric cord? Maybe a 25ft RV extension cord too?