Realistically it tends to average around 85-95Mbps. In my neighborhood we have fiber-to-the-home with 100Mbps synchronous speeds. I’m a bit of a pixel peeper (thanks media OCD), so for big screen viewing I must Direct Play BD-rips. All media on my NAS is in MKV containers, BD-rips with all audio and subtitle tracks. I also have an off-site backup in the cloud with Backblaze where I store all our personal files, photos, videos, and more recently all the media from my NAS.
For the purposes of a local backup I use 4x4TB WD MyBook external USB3 drives. Media is stored on a 4-bay NAS (WD My Cloud EX4100) using 4x4TB WD Red drives, also hard-wired to the router. I decided to focus spending on a new OLED TV rather than upgrade my PMS.
I use a late-2013 quad-core i5 iMac for my PMS hard-wired to the router. You be the judge, as I’ve come to learn that one person’s modest approach is another person’s high end! I’m happy to share mine, which lands a bit on the modest side (at least in terms of CPU). I know some Plex employees have pretty beefy systems while others have more modest setups.