Here’s my take on solving the filament path / tension issue on my Ender 3. I noticed that some of my prints had diagonal lines on the top layers as the extruder was struggling to pull filament into the feed hole at a consistent pace. When there was tension, I got 10% or 15% under extrusion.
I came up with this design to address problems I found in mounting the other “2020” filament guide on my X gantry. The bungs broke almost immediately since I printed the parts in PLA. This version slides over the top of your spool holder (the metal part). Just un-screw one of the “nuts” holding the roller to the metal piece and slide this guide over top. It should be a tight fit, which keeps it from wobbling around. The straight part should rest on the top of your frame, making for a much smaller profile piece.
This part works great with an extruder intake guide like this one: https://www.thingiverse.com/thing:2873157
I sliced mine with Simplify3d, with 20% infill and 3 perimeters. My machine is now pretty tight in terms of dimensional accuracy – if you can’t fit the guide over your spool holder, just file it a bit. The fitting should be tight but should not look like it is stressed or “bulging”. Make sure you are extruding enough as the stock settings can be quite off from the factory.