I have used goose quills with an appalachian dulcimer, mostly because a goose owned by a friend shed a load of flight feathers. I trimmed the nib at an angle like pen making. The sound was gentler than a plectrum. What I found was the feather being less durable than plastic tends to fray at the end, but the frayed edges can be trimmed back to give fresh quill a number of times before the feather has to be abandoned.
When pens were made from feathers, I believe they were hardened by inserting the point into hot sand. I did not, however experiment to see what effect this might have on a musical quill.
As for removing the rest of the feather, the longer the bit that sticks out, the more likely it is to catch on things, slow the movement of the point or be a nuisance. That said, a long untrimmed feather looks good, so it depends on how you want to look. Real quill pens were trimmed, it is only the ones in films and on book covers that stay feathered.

Quack!
GtD.