The high road: Tails
A whole operating system that forgets everything when you shut down.
Tor Browser protects your traffic. It does not protect the machine underneath it, which is still your everyday operating system talking to its usual services in the background. Tails is the high road that closes that gap.
What Tails is
Tails is a complete operating system that boots from a USB stick, routes everything through Tor, and forgets everything the moment you shut down. Nothing is written to the machine's own disk. When the session ends there is no trace of it on the hardware, which is a very different guarantee from a browser running on top of a normal system.
What it protects against
The amnesic design means a device that is later examined carries no record of the session. Routing everything through Tor means no application can accidentally reach the network outside Tor. Together they cover the failure modes that Tor Browser alone leaves open, which are the machine remembering and some other program talking around Tor.
When it is worth it
For casual reading, Tor Browser on your normal system is fine. For anything where the machine remembering the session is a risk you care about, Tails is the tool. It takes a USB stick and a few minutes to set up, and after that it is boot, use, shut down.
The atlas does not require Tails to read a plate. It recommends Tails for anyone whose threat model includes their own hardware being examined later.