Didn't read the thread, but most combination modem+router devices don't have a QoS setting to prevent a single device from hogging all the upload capacity and killing Internet service for the entire household. I have always preferred to have 2 separate devices, but my current setup doesn't allow it. I have an Arris all-in-one multi-room DVR system where the main gateway unit has a DOCSIS3 cable modem, MTA (can enable phone service, inactive), 802.11ac WiFi router, 5 tuners, and DVR storage (not sure of the HDD capacity).
I have disabled the built-in WiFi and I use my own wireless router in bridged/access-point mode, but I have no way to limit upload and I just have to be aware of what's happening when a YouTube upload kills Inet or an Apple device on charge is uploading to iCloud Photo Library.