Mizani says there are eight curl types based on their 2012 Natural Curl Key.
Sisterlocks teaches about 18 different hair types in their four day training class.
I say that both companies are falling short on the number of different hair types walking around in the world.
Please note, that shallow curl patterns can NOT be texturized because the curl pattern will go from "shallow" to just plain "straight." There is no middle of the road with shallow curl patterns.
If you have a deep curl pattern, then a texturizer will make a deep set into a shallow curl pattern.
If you are not sure of whether or not your curl pattern is deep or shallow, then grab your natural hair and slightly stretch or elongate it. If it still has a wave to it, then you have a deep curl pattern. If it looks straight with minimal stretching, then your curl pattern is shallow.
Now, shallow curl patterns can be resistant or stiff despite the fact that they are close to straight as far as curl patterns go. The resistance factor is how strong the hair proteins want to remain undisturbed. On the flip side, a deep curl pattern is possible that it is pliable and easily straightened.
Resistant hair whether deep or shallow will resist being straightened by heat and will resist being straightened by chemical.
Some resistant hair if texturized will eventually reform into its original protein bonds as if the chemical never even took. So for some resistant hair, if you do not completely "knock" the "kinks" out of the hair, it will revert back. Also, please understand that if you are going against the resistant hair trying to straighten it with chemicals or heat, you stand the risk of making it fragile, but it will be straight.
In my opinion, once someone determines that they have truly resistant hair whether it is a 3/4" curl diameter or 3/8" curl diameter, micro-locking by coiling or interlocking should be presented as an option. Resistant hair will less likely maintain long straight lengths because it will be pre-deposited to breakage due to the processing required to "knock" the kink out of it.
Roller set/wet set are still the best secret to maintaining length, but the hair has to be straight enough to wrap around the roller in a smooth manner which goes back to how effective the relaxer took.
If you have pliable, soft, manageable hair, then maintenance is much easier because the hair is NOT resistant to change.
I would like to conclude with a real life Q and A scenario:
I am rethinking going natural. It took me too many hours to wash and straighten my hair. As soon as I finish a few sections, the first ones are back to poof a ball again. I am eight months post relaxer, and it has been rough.
Everyone's curl pattern and curl behavior in regards to shrinkage is different. So everyone's natural journey is unique to their hair's unique makeup. I have seen soooo many different natural hairtypes in my chair that I can safely say that there are probably 40 different natural hair types. Based on the scenario that you just described, you need two different products to moisturize/stretch then seal it with a defining gel for control. If that does not work, then you need to consider micro-locking by coiling or interlocking. If your hair is as resistant to straightening as you described, then you will damage it in order to make it hold straight. Be true to thine self. I have seen darker skinned sisters with loose curl patterns and lighter skinned sisters with ultra coily hair. Your hair knows what it wants to do. You either work with it or against it. After eight months post relaxer, you should know if you can control your hair without locking and without chemicals. It's all about control. Otherwise, you start the day with one style and by the end of the day, you are trying to figure out why there's nothing left of the style. More bad hair days than good hair days are a definitely a sign for change.