Browser Automation Studio can hold up to 300 threads with browser and up to 2000 threads without browser.
Threads with browser in fact is not threads, but processes.
It means, that every browser run in different process.
If browser process will crush, main process will restart it immediately.
In average every browser process can use from 50mb up to 200mb of ram.
BAS tries to minimize memory and cpu usage as much as possible. On thread restart, browser process will be asked to clear browser data instead of restart process.