I have heard of #[3]​ but not used it! On nostr the experience is quite variable both in terms of features and customizability. Some clients like Damus allow you to customize your relay list but all your content goes to all relays. Others like Nos may let you publish content to a specific relay for each note, and others that want to be more user friendly may take the relay management piece completely out of the users hands. The nice thing is that as long as you have your private key you can test different clients though people have run into some issues like losing their contact list if you try to jump between some clients too quickly. There are tools to fix those issues so I wouldn’t let that dissuade you from exploring!