Here in the UK you can use Messages[0](the default SMS app) for chat. It supports RCS. You can send pictures, emojis or even use for group chat.

[0] https://play.google.com/store/apps/details?id=com.google.and...

Current availability: Chat features in your Messages app are available in France, Mexico, South Africa, Spain, the UK and the US, and across multiple operators globally. We are working on bringing chat features broadly to more regions, operators and other messaging apps (e.g. Samsung Messages).