I have never gotten into the notching thing, although I see where some folks that make their own calls only cut the angle off of one side. I assume that is so they can feel the call in the dark, if needed, to know which side is up.
Personally, I carry a LOT of mouth calls with me when hunting, although I generally only stick with a couple of them while calling,...one for those early morning roost situations that I want to make those really "nasally" tree yelps with, and one that will make the more aggressive yelps and cutts which I will switch to after they come out of the tree and throughout the day.
I have a couple of those plastic containers with three of four slots for individual calls. Before the season, and before I go hunting, I will prioritize the calls in the slots in one of those containers so I know exactly which ones I want to use at any given time. (Most all of my calls are color-coded with different colored tapes and/or reed color combinations)
The calls in the remaining slots and containers are of two types: one type is the "back-ups" for my first two primary calls, and the other type are my secondary choices, and those calls usually have some sound characteristics that vary from my primary choices.
...Now, going beyond the original question a bit to explain my personal "theories":
I also carry at least one "general container" of mouth calls of various sorts. Those are the calls that aren't quite making the grade for my primary containers, but that I can entertain myself with when I might be bored due to inaction. Those calls rarely come out, but to be sure, there have been those admittedly rare instances where I have pulled them out and started playing around with them, had a gobbler suddenly answer one of those calls, and ended up with a dead turkey over my shoulder.
Here's the explanation for why I carry so many mouth calls: I am a firm believer that 1) turkeys have different voices (just like humans), and 2) gobblers (and hens) can identify the voices of the turkeys that they "hang with". I want to be able to cover that general spectrum of turkey voices as much as possible when I am hunting. Carrying an assortment of mouth calls with different pitch and tone characteristics allows me to possibly find one of those specific hen voices more easily.
Having said the above, one would logically ask,..."Why, if you believe turkeys have different voices, do you stick with the two primary calls you said you use to start with? You are contradicting yourself."
...Good point! The answer is that I also believe that most turkeys fall between a certain range of "voices", in general. I always want to start out with staying within that range,...and quite honestly, it is usually pretty difficult for me to abandon sticking to something within what I consider to be that range. Over the years, I have just witnessed too many instances of turkeys responding to "turkey voices" that I never thought they would respond to, to discount not trying something out of the ordinary once in a while.
....Okay, so I got kind of carried away on the question,...I never claimed to be "short-winded"...
