I just read that there are four different types of authentication methodologies that can be implemented:
I would like to know how difficult it is to switch from one method to the other once we have implemented a method. So if we choose to go ahead with custom users (as there are very few users now) and then decide to switch to some other method, how difficult will it be to change it?
No very difficult at all. The biggest pain will be having to remove any allocated licenses etc and then re-allocate them to the users new usernames. (Eg. removing from CUSTOM\USER1 and allocating to MYDOMAIN\USER1)