My problem with using a pot to boil nebulizer cups I would get busy and forget about the pot. I think s lot of Mr cups got too hot of boiled too long & were quickly destroyed.
Zero filter. I use the largest one and the largest container. It also comes with a digital meter that shows many particles a million are in the water after filtering. It is amazing ! When it gets to a certain ppm then you are ti put a new filter in .
I buy filter 6 at the time. 6 will lady me at least 6 to 9.months