Signal does stay in sync between my laptop and phone, but I think if I wanted more than that it would not be easy to achieve. Message editing was added in a recent update, and it seems to be as easy to send photos via Signal as any other messaging app (I can't remember if it was ever difficult).

I've become more insistent about E2EE for anything I rely on lately because big platforms have been scanning "private" conversations for content some computer program guesses violates their policies. Someone I know recently got a suspension from Facebook (yes, they're probably worse than other platforms) for a joke sent to a friend in chat years prior. That took it from an abstract they could to a concrete they do.