Integration with External Data

Is anyone familiar with how appsheet integrates with tables that connect to external data sources?
Take a look at below picture.
Our company has their own system, but unfortunately the system is not accessible to see the data when we really need it (on the field).

However they have setup excel table queries that connects to the system via external data setup.

I would like Appsheet to connect to the sheet so that our sales guys can at least have access to the info in the field.
In theory all I have to do is refresh the table and any new info is added.
I was however wondering what would happen if I manually added customers via the app and as well as the through our system.
Is it possible to set it up that the data added in manually is not over written?
I see that there are 3 options on the external data properties window in the picture provided below.
Is anyone familiar with these options and if one of them in particular will do what I would like?

I found another interesting article referring to these option, but I thought I would ask the community 1st what there thoughts are.
Data Range Properties Options

Hi, @Michael_Pinto, was wondering if you got this to work?

Nope. Seems like the data gets written over. I don’t seem to be able to intergrate both.