You hit nail on head with NEGHL. The thing to remember for all these programs(yes some are way bigger than others) is that National at each age group is considered Elite/tier 1 in the girls game (there is no diff like in boys between T1 and elite) The American whether it be upper/middle/lower (that all depends on how many teams, etc.) are all tier 2.
Anything below that you are exactly right that it is same as town (tier 3) girls hockey and the only reason to do is if A. you have money to burn and/or want the better ice times that town teams don't have (ya know 6 am games) as well as to say your girl plays in a more structured and of course organization.
Now here's the other thing to be mindful of. There is a tier 1 and 2 state tournament at end of years. Other states outside of mass have same thing called regionals. HOWEVER, each organization can ONLY send 1 team per tier to states/regionals. So you will never see 2 breakers or wizards in tier 1 as that is reserved for each programs top team and is legit. Typically those teams the better ones anyway are 'mostly' made up of the older birth year (another difference from boys in that in each group you can have the better of the 2 age groups playing for top team) but it usually is the older ones. At tier 2 this is where you need to be careful. Many of the bigger programs list like 2 or 3 tier 2 teams yet only 1 can get into the states/regionals. the better one is typically mostly made up of the better younger year girls kind of like a pipeline for next years tier 1. So if a team has 2-3 tier 2 teams in the AMERICAN hope you get the one with the higher slot of the group bc that will be the one that goes to states, the others sit home and are really paychecks on skates...They also will play in less competive tourneys during the season.