Bitwarden has had some performance issues in the past with managing larger (>~250) logins, but they've been greatly improved in the last few months and I no longer have an issue. My password database currently contains 870 logins.

Bitwarden's support via IRC/gitter was exceptional when I was experiencing issues with it. Not only did they fix the problem, but they provided a custom build for me with more verbose logging enabled and worked with me directly to figure out what the issue was. It was fixed in a couple of hours and I was able to run the patched build without issue until the fix had been merged and released.