As to buying separate collars, here is my experience.
I tried them. I got it of my system.
Unless you have the collar highly starched and polished, a soft detachable collar will look no different from a regular one. The old world look can only be accomplished with the starch and polishing.
I found the collars uncomfortable with the collar pins poking me in the throat and back of the neck. I also had one shirt where the collar did not align perfectly with the shirt band.