There seems to be a lot of questions arount Radios, let me see if I can help!  

CB (Citizens Band) Radios: 
        There radios started in the 1940s with 23 channels, in 1977 channels were added brining the total to 40 channels. 
        These radios are limited to 4 watts of output (AM) or 12 watts output (Single SideBand), and no license is required. 

GMRS (General Mobile Radio Service): 
       These radios started around 1987 and have 22 channels. 
       These radios have a maximum of 50 watts of output  (UHF)  
       They typically also include the FRS (Family Radio Service) frequencies (channels).  
       If you use the channels with 2 watts output or less, you are considered FRS and no license is required.  
       If you use these channels wit more than 2 watts output (50W max) you are considered GMRS and are required to get an FCC license for your family (no test) https://apps.fcc.gov/coresWeb/publicHome.do  

Ok, so those are the two most popular radios for the general public. Now we need to discuss output wattage (range).

Range:
These types of radios we typically refer to as "line of sight" signals. Meaning for optimal use, there should be no obstruchtions between the two radios trying to communicate.
A 2 watt radio, on the water could communicate a mile, but put trees or other obsticles in between, and it could be 1/4 of a mile.
So the more wattage you have the farther you can "talk", and get through obsticles.
But keep in mind, if I have a 40 watt radio, people can here me miles away, but if they have less wattage and respond, I will never hear them because their signal will not make it back to me.
If you are in the bottom of a "holler" (valley) only people down there with you will here you regardless of how many watts of power you have. People on the other side hill will not hear you (line of sight rule).

So what should you get???

If you are traveling in a group, and just want to talk to each other, a small handheld should suffice.

If you want it in case of emergency, go big. 40 watts seems to be a good buy, if you go up in wattage from there, they start getting very expensive and i'm not sure if the extra 10 watts is worth it.

For emergency situations I like SPOT, its a statelite based system where you can request rescue. I use the Spot-X when ever I am out of cell phone range.
More info here: https://www.findmespot.com/en/

Here are some radio vendors I have seen recommended on FaceBook

Betner Communications LLC

Cardo Communication

Chatter Box 

SXS Radios