There is more at "play" when discussing how "restrictive" or how much "resistance" there is in any given pipe.
IMHO "restrictive" refers to air passages through shank and or stem. While "resistance" refers towards how the pipe was packed and or the style and type of tobacco, combined with the humidity of the chosen blend.
As far as the "resistance" factor, you are in control of the variables, by how you pack, how humid / dry said blend is, and type / style of tobacco selected.
"Restrictive" is subjective, since we all have our own preferences. Too "tight" to one may be "perfect" or too "open" to someone else. Of course the opposites might also be correct.
Personally, I lean towards what many might consider an "open" draw. Air passage in the shanks drilled to 4mm, and stem drilled to 3.8 - 4mm. These I believe are close to what Rick Newcombe prefers, but not as "open". Almost every pipe I currently own has been "adjusted" ( by me ) to these specifications. There are a few exceptions, since the pipe carver knew in advance my preference and took that into account when creating said pipes, for me.
My main blend of choice is Escudo, which I semi rub out. Not completely to ribbon, but maybe half way to ribbon, if that makes sense. As far as humidity, I check to see if the tobacco is "springy". To check, I gently squeeze the blend between my thumb and first two fingers. IF it stays "clumped" up, I let it dry a little. IF it gently "un furls" as I release my thumb and fingers, it's just right, for me.
The "method" in which I pack my pipes, combined with the drilling dimensions works for me. It has taken me decades of trial and error to find just the right "combination" of all the above, so each and every pipe smokes well, for me.
IF you believe that "opening" an air passage in the shank or stem may yield a more enjoyable smoke, I suggest you make any adjustments in very tiny increments. Once you remove material, you can't put it back. IF you go too far you will get an "airy" experience. You may find flavor loss. Sometimes you may be able to adjust the draw with tighter packing, but not always. Be prepared and willing to F up a number of pipes trying to find just that right drilling dimension combination, for you.
Before you decide to redrill anything, I would first check the slot in the stem. IMHO that is the area most "restriction" resides. Sometimes all it takes is to open the slot to a slightly move V shape to get the desired results.
Before I finalize the purchase of any pipe I take a standard BJ Long pipe cleaner and insert it through the stem and shank. By the "feel" I am able to tell IF the drilling dimensions are close to what I prefer.
Sorry for the long winded explanation. This subject could have a full chapter dedicated to it, in a How To Smoke a Pipe book......