you are very correct in your frustration... there is noo standard measurements for ratings things like skimmers/filters etc...
the biggest problem is not so much the equipment you want 'measured'/quantified, but rather the system it is being used on..
If you are going to have the exact same system, with the same livestock, and the same rocks and sand, and clean / maintain it hte same as the other guy, then yes, maybe there can be some standard, but, i have not ever seen two systems that were the same...
Everyone does things different.. they keep the water temp different, they keep the pH different, etc...
Try not to focus on the minum maximum info, and go for the average...
If you try it out for a while, and find you dont like it, then you can try something else...
Everything is replaceable and substituable... including information...
If you over think every component, you might not ever be happy...
The big thing that most folks like is the ability to upgrade, and substitute to fit your needs, your ability to get stuff, and your budget...
The things to focus on are how much maintenance you want to do, how often, how much money you want to spend on utilitys/ electricty bill, etc...
i usually dont reccomend hang on filters, or cannister filters as they are limiting to what you can do, and require more maintenance then a regular sump/refugium...
This also allows you to get all the ugly equipment out of site and makes your display tank only display fish and critters, not heaters and skimmers...
But, i also understand that a sump seems more complicated and intimidating to those just starting out...
I also suggest getting an aquarium controller right off, instead of buying timers and power strips and heater/fan controllers..
the aquarium controller maybe a few bucks more then the other stuff, but, it is more accurate and more options/controllability then the odds and ends timers you get at home depot or whereever...
And folks usually migrate to aquarium controllers anyways, and buying it upfront will save you time and MONEY...
but most other things can be upgraded later on, and you can usually find folks to buy your used equipment to offset the costs of the new equipment...
anyways, i feel for you, but please dont let your frustration overwhelm you... just be satisfied knowing that no matter what you do, someone has already done before you, and it worked for them...
good luck