Is it the only configuration we needed to activate the NAT?
Yes, that is the only client side configuration you require. On the WinGate server you need to have the extended networking installed, which is done at the time of installation; sounds like you have it so you are ready to go.
How about other tab-sheet, such as firewall, port security, routing, etc?
Firewall, defaults shoud be fine.
Port Securtiy, used for port connections in or out of your network. Generally you do not require any thing for traffic leaving your LAN at a simple level. If you were running a web server on the WinGate computer, you would probably want to open up port 80 to allow connections to your own web server.
Routing, you should not need to worry about that in a simple network as well.
How many NIC we need for Proxy Server
1... Please note, you can still use the proxies while having NAT, even if you do not have the settings set in Internet Explorer. We have a feature called "Transparent Proxies", it will catch any web traffic on specified ports passing through NAT ... and hence allow you to... for example ...
1. Scan web traffic with the Kapersky Antivirus Plugin for WinGate
2. Scan web traffic for objectionalbe material, with the PureSight plugin for WinGate.
3. Allow you to benefit from using the cache.
* Transparent proxies are enabled via the WWW Proxy Service --> Sessions