Conversations is a gold standard in XMPP-world and arguably the only reason XMPP is alive at this point. One can complain about some default choices taken there but thereโs no question that Conversations strives to be modern, user-friendly and secure at the same time and itโs doing great. Iโm running my entire family on it and theyโre very happy.
Just make sure the server youโre using is being properly maintained: https://compliance.conversations.im/
Yaxim is a tool for old-school XMPP nerds. Nothing wrong with that it just has this 2000s flavor. I would totally not recommend Yaxim for normal people as itโs not as maintained as Conversations and targetted at a specialized XMPP users.
Just go with what Conversations is recommending. That means OMEMO. If you'd like to read in more detail about it I recommend: https://github.com/siacs/Conversations#security
Also, Iโm not sure whatโs your relationship with privacytools.io but Mikaela knows a lot about practical XMPP so you may want to get it touch with her too: https://social.privacytools.io/@mikaela