I know this is old, so sorry if new info came to light by the time I write this, however there are MANY benefits (AND downsides!) to Orbot Tethering!
As stated previously, forcing a device to route all traffic through Tor can be very difficult. In fact, this is why some people choose Tails OS as you said before.
And of course you don't have the rights to set-up/configure the network. That's the point of Tor. Preventing those that have control of the networks from peering in to the private connection. Tails doesn't need access to the router to be secure, and neither does Orbot.
For the Tor-through-Tor, this is a great misunderstanding... Orbot as a hotspot is similar to Tails as an OS. You no longer inherently need the Tor-Browser-Bundle at all for Tor access (Tails still does for consistency, but that "Tor" doesn't double-route you because it knows it's running through Tails. This can be proven by installing another browser and testing the IP)
Keep in mind, the above fact has drawbacks too.
Exit relays can attempt to image your traffic, and if you make "clearnet" logins, your entire Tor Circuit is potentially thwarted.
You can read more by finding the 3rd attack technique here (The article is technically about Torrents but the 3rd attack explains in further detail the drawbacks): https://blog.torproject.org/bittorrent-over-tor-isnt-good-idea/
The easiest way to think of the usage is by looking at today's setup.
-Tor Browser for Android is like the Tor-Browser-Bundle, strictly routing browser traffic through Tor and nothing else.
-Orbot works like Tails at the network level, enforcing all traffic goes through the Tor Chain at a "router" level (or VPN locally) instead of an OS level.
Hopefully my answer wasn't too long and confusing... Happy connecting!