Electronic air cleaner vs pleated filters
You will still want a particulate filter at the intake, I was taught to put particulate filters at each inlet position this helps keep the ductwork clean and prevent build up in the heat exchanger.
Electronic filters are the next best thing in my opinion but just like a 4” MERV 8 they need to be replaced regularly, the electronic take a few minutes to clean. The mesh grid helps with the particulate matter much like the dust filters at the intake but the air flowing through the mesh takes the air to a discharged level, now the air passes over the high voltage grid and the Remaining dust - pollen , mold spores and even smoke particles are trapped in the static grid.
There is very little resistance to air flow and these are effective at cleaning the air as long as they are regularly cleaned.
My last home I installed this system because of a granddaughter that had severe asthma, this system kept the air in the house clean and inside she never had attacks, I pulled the mesh and grid panels once a month and rinsed them in a shower, it is amazing how much dirt was on them every month. I replaced the 3 pre filters (cheap fiberglass Every 3 months) If I had not seen seen the amount of dirt coming off the electronic grid I would not have beloved how well that system worked, we really noticed when the valley was filled with smoke and my granddaughter was fine inside the house I noticed the system starting buzzing only 2 weeks after cleaning I pulled them and cleaned again they were pulling all the smoke from the fires out of the air I was impressed with how much the system removed from the air, I did run the air handler 24/7 when our granddaughter was with us and she had less need for a nebulizer and fewer trips to the ER so I recommend them for that reason but yes they have less resistance than a high MERV filter.