A lot of the protected “button top” cells on fast techs site are quite long (close to 70mm). That might be a dealbreaker for you as they do not fit in some lights.
I have had fitment issues on a few lights and ended up slightly denting the protection circuit on the bottom of one of the batteries. Which lights are you looking to use them in? Selfbuilt on CPF usually reviews which batteries fit and dont fit in many production lights.
Im not sure what the difference between ncr and icr li-ion chemistry is, so maybe someone else can explain that.
The prices vary depending on capacity and brand. Really how much capacity you need depends on your application. If you want long runtime then you would be looking for a 3100mah or 3400mah cell. If runtime doesnt matter and you just want a good battery I would recommend the sanyo 2600mah or panasonic 2900mah as these are in my opinion the biggest bang for the buck.
Both sanyo and panasonic make very good quality batteries.
Dont forget to try coupon code BLF and or PRICECONTROL in the my cart page for a discount!