I've used pellets in the nylon bags with no issues. When using the fine mesh bags nothing should escape that would cause a clog. Of course there are always variables where someone else may have different results.
It takes a lot to clog a poppet. For example I ferment in corny kegs and use the gas disconnects for the blowoff tubes. Even when there is a lot of blowoff there is never a fatal clog. When pumping out, sometimes there is a lot of yeast slurry before the beer flows, but it still flows.
Avoid the muslin bags and other stretchy larger mesh bags.I'm sure they must be good for grains or something but useless for anything I've used them for. Nylon bags just clean up with the garden hose or in the sink and can last for a long time if cared for. They are also good in the boil for containing pellets when larger loads are needed that can clog the plumbing :-)