You are going to have to go android. I will refrain from commenting on apple. I have a Pi 400 but just isn't as good as a dedicated android streimer.
I use the Nvidia Shield, Logitech K830 keyboard. I have kingston SSD in a 2.5" sata external case for cheap storage since had it available. But you want cheep grab a 4k amazon stick or Mi box. You can use an OTG dongle with ethernet USB splitter and have ethernet, usb for storage, keyboard etcetera.
https://www.amazon.com/AuviPal-Powered-Adapter-Charging-Streaming/dp/B07TX8FY6W
Powered is what I used.
You're not going to get 1000 Mbps, because the micro usb is a bottleneck. Most hubs will only give you around 90-100Mbps. But the theoretical max is around 480Mbps for micro usb.
You're overthinking the setup, and issues that shouldn't occur (unless you get the wrong OTG cable or hub). The OTG cable is the link between the hub and firestick, and where you provide the power to. The male micro usb end plugs into your firestick, the female micro usb end plugs into your power supply, and the usb A end plugs into the hub. As long as you're not trying to connect a devices that requires its own power supply (ex. external harddrive or bluray drive,) this is all you need to do.
A lot of people recommend this one: https://www.amazon.com/UGREEN-Ethernet-Adapter-Converter-Chromebook-dp-B07TWGHM99/dp/B07TWGHM99
Seems pretty hit or miss though. Some claiming they only get 100Mbps, while others claim in the 300Mbps range. Also note that right on the listing, it says not to use the micro usb slot on the hub to power the firestick. You have to power the firestick through the OTG cable.