Then in your case, only multi-inventory sourcing feature can definitely work out which is there as by default in bagisto.
Regarding getting notification for low stock, some customisation is required.
That seems great. Let us know what all the help you need from our side. Also, would it be possible to connect on Skype to discuss further more on this?
You can connect us here: https://join.skype.com/invite/PcxhAmHq0o7C
The last php version on which bagisto works is 7.2