Hi Andres,
Many questions,
Long answers to be sharp.
Being really honnest, (and not selling anything) I found the NXP video on those topics really cool and clear.
https://www.nxp.com/video/lesson-0-an-introduction-to-the-course-and-meet-your-trainer:LESSON-0-KW41...
Lessons 6 to 9 will give detailed answers to your questions - Is quite long, maybe you can skip some sections.
Short anwers:
- Thread = BLE with mesh: no. .
- Typically BLE mesh, Zigbee and Thread are competing technologies. Each is offering a different compromise (Power, range, security, IPv6, payload....)
- From communication distance they are ballpark all 3 the same (not considering all variants, optimizations... in the range of 10m)
- Can you have 2 devices communication in Thread wo Gateway: Yes.
We will do our best to release Zigbee functional example asap.