I know most bookers use text only but is there a way to prevent iMessages from popping up on every device? Had a booker send an iMessage the other day when I had sent them a text originally.

On the devices you dont want imessage on go to settings - messages - and just click the slider that enables imessage

give the phone number you use for work or with family and friends to a booker or provider.  ALWAYS have a second phone for your hobby.

Does anyone else use those apps that give a second line? Like Google phone or whatever

I use the Sideline App on my Android