If you are already in a group you can send a message to them. You need an app to do it and pay a few quid. 1. Get wear installer from Google play, install it on your watch and phone, and Learn how to sideload apps. Then you can sideload a Google wear os app called wear messages, by downloading it on your phone, then use wear installer to sideload it to your watch. Using this app it will store messages/groups on your watch when they send you a message so you can push a message to them at will rather than reply to a message and that's it. I paid about £2.50 for the messages app, although it does have some functionality without paying. 2. Other option is Informer: messages for wear os. Pretty much same functionality but it's about £4.50 per year, but you don't need to do any sideloading.
Also for first option it can be used for telegram, Facebook messenger, WhatsApp and sms if you like. Informer does it for more apps