(kiwiirc.com dev here) You might want to take a look at irccloud.com and kiwiirc.com/nextclient
These 2 clients cover most of your use case while others such as end to end encryption are currently being developed. Hopefully with with irc.com support multiple IRC clients can be reaching all of these features and in a standard open way.
These 2 clients cover most of your use case while others such as end to end encryption are currently being developed. Hopefully with with irc.com support multiple IRC clients can be reaching all of these features and in a standard open way.