To me the ultimate grouse gun would have two triggers with the right barrel open and the left barrel tight. I’ve had several guns in 20, 16, and 12 gage ordered by hunters in the northeast (presumably grouse hunters) which were ordered in just that way. My current favorite upland gun is a 6# 4oz 26" 12 gage DHE ordered IC/Full (.003/.028). I have the exact same gun in a 16 gage O frame at 6#s even that I shot very well for several seasons until one day I notice it was cast for a lefty. I have lost confidence and now rarely shoot it. That’s now the one I let the wife use. She will never notice.