The subject of oil filters has come up many times on this forum.
A filter is a jillion little holes tied together, and each hole captures one
particle of crud, then its job is done. A few years ago I did some research
on oil filters and found they were pretty much all 25 micron, meaning a
.025mm particle is the smallest they will catch. Apparently the oil and
filter and engine design people have figured out that 25 microns is a good compromise size.
Larger would let bigger particles through and smaller would restrict oil
flow. So to catch more particles you make more holes, i.e. more surface
area, more pleats in your filter.
The question of canister leakage involves getting the right sealing rings and being sure your sealing surfaces are clean and undamaged. We have covered that here. Part of the confusion is due to the substitution of wrong and unsuitable filter heads on some blocks. Here is a thread on the subject.