The pine64 Pinecil is a great starter soldering iron.
You’ve already received some great suggestions. Another one is Netdata. Personally, I use glances to collect the data and Home Assistant to display the dashboard. But I only do this because I already had Home Assistant running.
Latency tested using librespeed.org is about 50 ms.
How “big” are your movies and tv shows? If they are 4k UHD remuxes then Nvidia Shield Pro or Apple TV 4k behind a firewall to block external internet is your best option for performance, usability, and privacy. You will want to ocassionally allow it internet for software updates. Kodi, a mini pc, raspberry pi, etc. would be more private but you trade off a seamless remote, easy interface, and streaming codecs (e.g., dolby vision).