notifications send with ble_gatts_notify_custom() proper usage

[nikitos1550]

Hello!

Nimble is used under GNU/Linux.
I am getting data in separate stream and I want to send data through notifications. Sometimes I can get a lot of data, I am packing data to small 20 bytes packages and invoking ble_gatts_notify_custom().

Is it ok to invoke ble_gatts_notify_custom() from separate thread, not nimble host thread?
How much data can I push via ble_gatts_notify_custom()? As there is no any success notification sent callback/event, also not clear how big is queue in nimble internals, so not clear how to use api from this point of view/