Now that I have a 1Password account, do I need the 1Password.agilebitskeychain file in my dropbox?

Welcome to the forum, @left3rd! All 1password.com accounts use the 1password.com service to sync, instead of Dropbox or iCloud. So the short answer is no, you don't need that Agile Keychain any longer.

A slightly longer answer would ask whether you're still using any local vaults that are NOT part of your 1password.com account? If so, they may be synced using this keychain you discovered in Dropbox. If you're certain you're using only your 1password.com vaults, then it's probably safe to delete the Agile Keychain. On the other hand, the keychain is fully encrypted, so it doesn't pose a particular risk. If you're not certain what it contains or whether you will need it in the future, you can certainly keep it. Maybe move it out of Dropbox into a folder in your Mac's desktop, just so that it's not "in the cloud."