I totally agree with wuliwong, infact I have never edited any design and have always used available ones(bootstrap) out of the box to save time as my motive as a developer is a clean working app than a beautiful app.
Go to the builder page, remove all but pills Go in to the _options.scss partial and tweak some more Optionally take all of what's left and then refactor to your liking
I'd claim you save some time with above and still get a fully customized button.
Regarding using something like Bootstrap "out of the box" is not something I'd personally want to do once getting my project into production...but again, I'm fine using for just prototyping and then tweaking the styles later. That said, to each is own