What is a Headshell and what does it do ?

At a minimum, you're generally going to have to adjust vertical tracking force for each cartridge, and usually anti-skating as well. Most cartridge have their own individual sweet spot within the recommende tracking force range.

Not mentioned up to this point, but it's waaaay easier to mount a cartridge on a detachable headshell AND significantly lower the risk of damaging the cantilever during the process.

Johnny53 ;
Is a "detachable" headshell different than what has been discussed so far ? Would it still be required to check the angles as mentioned above when swapping two of them around ?

Thank you

note that on some headshells there's the screw hole to mount extra weight. all to match one cartridge to another

You must set up each cart/headshell with a proper protractor (mint, geodesic, or various online printout), VTA, and tracking force. You will then be able to swap out cart/headshells with only a VTF & VTA adjustment ~ and sometimes with only a tracking force adjustment.

This is fairly obvious, but even if two different cartridges require the same tracking force they both will likely have a different self mass. In that case you still need to adjust VTF for each one. Heck you could have two of the same cart and they still may need a slightly different setup.

For best performance all the parameters should be checked and readjusted if necessary. This can be speed up if you take note of all the settings before removal, and write them down for next time. The only time a removable head shells saves you is the time it takes to remove the old cart and install the new one. About 2 mins. max.