One more possible thing to improve, I don't know if there is interest in supporting Gnome, but Gnome creates streams in BGRx format, which means it wouldn't mach your stream, if you want to support it you need to change it to something like :
":", pwType->format_video.format, "Ieu", pwType->video_format.RGBx, SPA_POD_PROP_ENUM(2, pwType_->video_format.RGBx, pwType_->video_format.BGRx)