1. I wouldn't bother with the Genie app, myself, it has a poor reputation on the usefulness and buginess end. I've had several Netgear routers and have never felt like I needed it...Our ISP download speed is about 200Mbps. I get about 200Mbps speed from clients connected to the satellite. Are you finding the speed of clients connected to the satellite limited? If not, I wouldn't worry about it.
2. I turned on IPv6 here for a about a day, and it worked just fine. I'm also on Comcast. Not sure what the problem is at your place.
3. Most router manufacturer's firmware that I'm acquainted with only allows you to change your password, not your user name. There is third party firmware that allows you to change your user name, but not for the Orbi.
4. I don't worry much about WPS these days...don't know if there's any current firmware where the past WPS exploits aren't prevented by various methods. On the other hand, there's nothing stopping you from opening an issue with Netgear, requesting control over client-facing WPS, if you feel that's necessary. Then you should find out if that's on their list of functionality to be added.
Yes, the firmware GUI is limited, but has gotten a little better with the latest release. More information on attached devices, etc. Plus added features and security fixes. I still miss having a log...but what I do like is that I haven't had to do any troubleshooting yet, so haven't really missed the monitoring tools that I'm used to. So far, the Orbi has just worked, been stable and provided great performance.
So you've had problems updating the firmware? Have you followed the directions on how to update the firmware in the release notes? Briefly, there's firmware for each unit that you need to download, and you update the satellite first. Then update the router unit. Curious where this process is failing for you? I haven't tried the automatic firmware update, I prefer more control over firmware updating.