Capos serve two very good purposes; allowing easier playing alongside other instruments and finding a comfortable range for your voice.

When I was a teenager with a very cheap acoustic guitar and no knowledge of setting a guitar up, let alone realise they could be, a capo also came in handy to lower the action and make the *^%!! thing playable.

Interestingly, and with a large guitar collection to play around with, I notice the drop off in good intonation as you get further up the neck more with some than others. One of my favourite guitars isn't really good with the capo beyond the 4th whilst another is still holding good tone and resonance way beyond a practical fret.

Lately, and with my "changing" voice in mind, I play a baritone guitar all the more. The principle, as a friend advised me at the time of purchase, is a backward capo..,,

I also tune a Rainsong I have to D to D. The carbon fibre neck keeps it in check.

One bit of advice from experience; Always have them just slightly tighter than buzzing.