Hi Borroz and thanks for your reply 
It is only a hobby project, so I don’t intend to send a lot of data, etc…
I am not planning to send much more than laptimes (coded in milliseconds or 10x milliseconds, that would be on 16bits). This would already be great.
In a second part, message exchange from the base could also be simplified (index of standard messages instead of custom text).
Could you point me where I could have more chances of finding answers?
Most of the questions also applies to LoraWan (antenna design and performance, hardware might also be the same).