Pidgin essentially stopped supporting new XMPP features a decade ago. This includes multi-device support and many new convenience features (delivery receipts, file uploads). There are some plugins that might be able to compensate, but at significant effort.

OTR wasn't made for the multi device use case at all (and even OTRv4 is explicitly single-device). If you happen to log in with multiple clients, it will most probably confuse the other side's OTR plugin