keysmith is the lighter tool compared to quill and the right tool for the job. It also allows you to derive multiple keys (.pem files) from the same seed with the -i <derivation index> option.
quill is more a replacement for and on the same level as dfx. Quill is for people who want to only do neuron management but with a simpler interface than dfx. Originally quill was used on top of keysmith. Only later was key derivation added directly into quill.
quill interacts with the IC, keysmith doesn’t. quill is overkill for what you are trying to achieve.