I already know all this. I was pointing out the flaw in the logic behind your assertion that any 18650 battery can be used in any 18650 mod and that "Circuit protection on your mod will protect your
device and detect the problem if something was to go wrong somehow because of the
batteries" it utterly false in ALL cases. And yes, ALL CASES DO MATTER.
First off, I don't believe the OP was asking if any and all 18650 batts would work/fit in his mod. I believe he was basically asking what other 18650s he could use. Your answer of any will work and the mod will protect you, is dangerous and not really in-line with the decade of battery safety vapers have been pushed down our throats.
Secondly, no mod, as far as I know, is intelligent enough to know when you are exceeding a battery's amp limit and therefore protects itself and the vaper from doing so and from the negative outcome that could bring about. Therefore, using "any battery" is not safe. If it were, we'd all be
vaping on Trustfires lol.
Besides, It's not wise to even trust a mod with the protections it does have. This is especially true with these cheap mainstream mods, but I would not put my faith in any mod, high-end or otherwise.