Fiberglass filters will protect the coil from the larger particles, but do not filter everything for a healthy environment. Unfortunately not all homeowners can use fiberglass filters as they may be highly sensitive to the environment. This is why some home owners and business not only prefer, but require pleated filters. That said not all units can handle the highest MERV filters. Pleated filters should be changed more frequently because as you mentioned they will bow and cause wear on the units. It all depends on the application, the unit capabilities and whether or not the unit was installed and sized correctly. For example some units are starved on the return. The basic rule of thumb is 144sq inches per ton, improper sizing and install can also greatly adjust the pressure. All of this should be considered. Fiberglass is not the only filter to use and neither is pleated. Again it depends on the application. Thanks for reaching out.

@@callmightymike Just MHO: Depending on everything, how clean you _need_ the air, or want the air, pets, having windows open, etc., don't go over MERV 8, and get room air purifies. Also, you can use two separate filters. Such as, where the first vent is at use a MERV 1, and at the furnace/AC, use a MERV 8, or lower, in conjunction with air purifies. As for the system itself, just don't restrict the air input, no matter what you decide. Myself: I would not go more than a MERV 6, I use two filters, and room air purifiers. *Yep, bottom line, it all depend on...!* EDIT As I am sure you two know, but here it is for whoever: (Well, my whole post is for whoever.) There are other multiple factors to consider. Such as, is the house well sealed, insulation, air transfer though outlets/switches, etc. And, of course, electrostatic filters are good. :-)