You can use AB Bypass mode and this will leave the insert active when the Program is bypassed: https://cdn.eventideaudio.com/manuals/h90/1.8.6/content/system-menu/global.html
Latency would be about the same if you are using 1 insert vs going through both paths of the H90.
You will need to enable Insert 1 for each Program to go through the Opus, so you may prefer the Dual Mode setup if you don’t want to do that.
