I'd pick one of the ones on the top row so I didn't have to stack them all again... they're gonna all get used anyway right?
It's not going to make much difference. People around here make mountains out of molehills. The main thing is recognize the service life of the filter and oil you use.
True indeed ^^^^^^^^^
A Wix air filter is a good choice... Or a STP premium air filter... Which is 98 percent efficient using the fine dust version of the ISO 5011 test. A much harder test vs the coarse dust test.