My device is a Roku Ultra (4640 series) installed June 2017.I recently upgraded my cable modem to Netgear's Nighthawk CAX80 (DOCSIS® 3.1 6Gbps Two-in-one Cable Modem + WiFi 6 Router). I have a 400 mbps internet with my cable provider and the CAX80 is capable of gigabit speeds. Since I upgraded, all streaming apps are loading/processing/buffering slower than before (not just 1 or 2 apps). I haven't noticed any issues once the show begins, but it takes a noticeable amount of time compared to my previous modem. I've tested my device on wifi and hard wired directly to the modem with a CAT7 cable and the issue has not improved. I've exhausted all troubleshooting with Netgear, as well as my internet provider. All firmware is up to date, all settings have been adjusted for 5G, I'm not using a VPN and both vendors confirm everything is working as designed.
Any guidance dealing with these new performance issues would be greatly appreciated, thank you!
1) You didnt mention your firmware version: Settings/System/About
2) Check for updates: Settings/System/System update/Check now - try again
3) Try the network connection reset: Settings/System/Advanced system settings/Network connection reset - try again
4) Turn off/use LOW setting for modem/router/gateway firewall - try again
Keep in mind 5G (mobile data standard) and 5Ghz (WiFi band) are two different things, and its important to make the distinction when talking about networking.
The answer is no - the new Express 4K ($30)/4K+ ($35) also support dual-band WiFi as well as the SS+ ($50).
As @renojim stated, there is no model capable of 400Mbps, and as far as Roku is concerned (though not LAN streaming enthusiasts) there is no need to, since "no streaming service uses such high speed" (which is arguable, considering YT).