for future readers, the setting is now shipped in >v0.49. The default is now back to GPT-4 as it has lower latency but you can manually change it to Claude 3 in settings if you wish to try out Anthropic's new model.
I noticed it might actually be a little more censored than the lmsys version. Lmsys seems more fine with roleplaying, while the one on Double doesn't really like it