not op and aware this may not be representive, but i share the preference for telegram as a just-works, "fun" and high-penetration messenger with whatsapp as a first and sms as second compatability fallback. this beeing in germany.

tg is light on resources like phone storage and bandwidth (and hence money) and has excellent multidevice support.

apart from that i don't belive one can have a seriously private conversation involving a device running popular versions of android/ios.