I've used a bunch of little bluetooth 4.0/4.1 receivers that my nice 3.5mm earbuds plug into.

Pretty much never had a problem with skipping or quality for any of those supporting apt-x.

This is true even when i'm also wearing a bluetooth watch, etc.

That's great, but also not the same as Bluetooth earbuds. I don't have trouble either with any kind of receiver that doesn't sit within my actual ear - presumably it's something to do with either additional signal attenuation, or lack of space for a sizable antenna, or both, but whatever the reason, getting rock-solid reception in a truly wireless earbud seems to be a very difficult problem to solve.

(If you're not sure what kind of device I'm talking about here, the Rowkin Mini is a good example - note the complete lack of protrusion beyond the pinna. I suppose the AirPods themselves don't really qualify by this standard, since they seem to have their antennae in the microphone boom which protrudes below the ear; on the other hand, I'm willing to tolerate such a protrusion if it's the only reasonable way to get good signal, and improved microphone pickup is a pretty good bonus besides.)