NIS/NAV and Thunderbird and Firefox

I currently use Thunderbird, Firefox and my IP is Comcast .

I have searched for answer concerning the compatibility between the two.

I am wondering if and when they will work together?

 

If I install NAV will I still be protected?

Does NIS have anything that is similar to Avasts Web Shield?

 

Any answer is helpful.

 

Thanks

 

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