If you look at standard efficiency filters, they represent very little restriction as long as they are kept clean. Put one in if you like. Yes, you can potentially have problems with restricted air flow. You can fail to make the sail switch or overheat the heat exchanger. The likelihood of causing a serious problem is pretty slim in my estimation, given how leaky (in terms of air
) the basement and utility area is.
I use Filtrete Hammock media. It is a cut to size, high efficiency, very thin media. It's hard to find, and none too cheap. I have it behind the return air grille.