If you wanted to do some kind of prioritization and bandwidth sharing and applying policies for different clients, that’d require some basic networking understanding and following documentation.
You could enable modem mode on the hub 3 and connect your computer directly to the modem and see how that works out for you.
Having a router in between is only necessary if you want to connect multiple devices.
Connecting to the internet is generally safe if you’re not running any network facing services on the machine, and even then, that should be safe as your computer (presumably running windows) should activate its firewall as if it were on a “public” network and not have file/desktop sharing ports open.
btw, I’m here in Ireland on virgin media, and have the same cable modem / hub, mine’s white instead of dark grey, but it looks the same, … I’ve been using it in modem mode from day one and never noticed any issues due to the modem… I’ve been having issues with the ISP once in a while, … internet stopping entirely, then coming back with horrible latencies and a weird IP address and 20Mbps throughput, … and then fixing itself, but it’s been perfectly fine most of the time.