Are these items essential?

Water pressure regulator is essencial. You can do damage right away without one.

Voltage thing? I do not have one. Thinking about that statement, I did have to repair my inverter to the tune of $450 when I plugged into a receptacle that was wired backwards (reversed neutral and hot lines on the receptacle at a RV park). Most inverters do not have a neutral to ground relay, but mine does, because I selected this inverter with this option factory installed.

50 to 30 amp adapter? I did need mine a few times. Once was at a RV park where the 30 amp receptacle was very loose, the contacts inside where worn out, and I was getting a 13 volt drop across the loose connection with a 15 amp load on the RV. So that is 13Volts X 15 amps or 195 watts dropped across my power plug. This is like having a toaster heat that connection, it was VERY hot.

The 50 amp receptacles have much more brass in them, the connections never seem to be failing, as they typically never see more than about 25 amps on them, 50% duty cycle. The typical 30 amp plug commonly sees 25 - 30 amps on them, so 100% duty cycle, and they overheat, then the brass weakens and will not hold the next RV plug tightly, so it will also overheat. This problem is commonly talked about on Rv.Net.

Your 50 to 30 amp adapter will stay in good shape (well better than the 30 amp plug in a RV park that is used 200 nights a year!) So it will keep giving you a good connection.

Another 'essential' that I do have is a voltage booster. Also a voltage monitor that stays plugged in all the time. So I know when the voltage is less than 110 volts, and I can plug in my booster.

One of the things that I am happy with, and patted myself on the back for installing is a 1 quart water accumulator on the pump. It makes the noise a lot less, and vibrations go away. $30. I installed it near the pump, and put a tee in the line connecting the pump to the fresh water system in the RV.

I also met a person who hooked up their RV at a RV park, and the hose had a huge 'bubble' in it after turning it on. I guess the water pressure there was about 100PSI. I hope that they did not damage any internal water lines, but the hose was not going to be used again. I always carry 2 or 3 water pressure regulators (until I leave one behind in a RV park). They are very cheap insurance.

I also carry a $12 water pressure gauge. IF the pressure is less than 40 PSI, installing a regulator can stop (well limit water flow) flow to the point that taking a shower is more like standing under a dribble. So if less than 40 PSI, I do not use the regulator. Flow is normal without it.

Have fun camping!

Fred.

Yes
Maybe
No

Flaguy

It depends on how you use your RV. I dry camp almost exclusively, so none of them are necessary to me.

I have the 50 and 30 and a 2 plug 15 in case I need it and have used it at my BILs to run 2 cords out the window to the AC.

None are "needs." And like insurance, odds are you don't need them. But same as insurance is cheaper than the consequence, if you don't have them but actually do need them the cost is much higher.

With that said, the 50/30 adaptor is a convenience so I would rank below the other two. Surge and pressure orotectors safeguard you in the background. I have both (I have several electrical adapters too) but have never actually needed either...that I know of :)

I own all 3

I assumed the OP meant they were looking at a 50 amp trailer and may camp where only 30 amp was available.

I've never had an issue getting 30 amp service at a CG.

you don't need insurance ether but most people have it

We have 2 out of 3. The surge protector and pressure regulator we bought/installed to protect things NOW. We haven't had trouble finding power for our 30amp trailer...no 50amp adapter needed.