I am not 100% but those bags look to be about the same mesh as the paint strainer bags at the home improvement stores. Correct me if I am wrong.
I just started doing BIAB. I have done 3 so far and my efficiency is getting better each time.(Thanks to you guys here at HBT) In fact I think it was my second or third batch, I will have to check the notes, but I hit in the low 80's. I am just using a 7.5g pot and I know this bag at the other stores would be too big but if it is a finer mesh than the paint strainer bags, I am all in. I have had a good amount of trub the last few times. Anywhere from 1/2 to 3/4 gallon
I am thinking I should chalk that up to the double crush though. Being new to the AG style and not seeing the levels of crush aside from the steeping grains, I assumed one pass on the LHBS mill would be good for AG and need the second run for BIAB. It may have been fine enough on the single run but I went ahead and did it twice as it seems to be a common recommendation. I may try on the brew this weekend to do a single crush to see if the amount of trub is less using the paint strainer bags. I just hope my efficiency is still decent. I guess its may be a catch 22. Good efficiency means more trub while low efficiency gives you less trub. Using the same style/brand bag of course.
As for the muslin bags. Are the holes on those considered to be WAY more coarse than a paint strainer bag??? All the muslin bags I have used, like the ones supplied in a Brewers Best kit are much more coarse than the paint strainer bag. In fact I used to use a paint strainer bag in my fermenter to do a fine "straining" after I cooled the wort.