Can we talk Tap on linux (mint/ubuntu)

[Thalium 4]

I'm not sure where to start on this one tbh.

I was sat looking at my comp the other day and came up with the idea of using my router firewall (multi OS boot PC) to reject the majority of unwanted traffic. At the moment on my linux mint install (I'm very new to linux - 2 weeks) this is done by iptables and similar setup on windows OS. With windows this isn't a problem as the tap adapter produces a MAC but on my linux install it uses Tun masquerading as my eth adapter IP/no MAC. 

I should probably first ask is there a need - it would make life easier and rejects traffic at the router reducing network load, a second(1st) line of leak defence if an accidental change is made?

I can't setup a firewall rule on my router (non wrt/tomato) that will give the restrictions needed without a separate MAC or IP to my physical adapter.

I have tried to setup a Tap adapter on my linux install and ultimately failed. I have tried (linux mint) using gnome network manager (bridge utils installed) ticking the box use tap and downloaded Airvpn config files (no extra lines at point of download) replacing the lines in the file after putting in directory 'dev tun' with 'dev tap0' along with bridge ip's etc and without. 

I did read somewhere I may need to change 'update-resolv-conf'... Basically I'm out of my depth without help at this stage and I didn't want to make the huge number of changes some articles I read gave guidance for without further advice and guidance.

In summary:

1- Will this indeed work well as a second leak protection measure?
2- Is it worth the effort?
3- Thoughts on the idea?
4- How do I change to use a Tap instead of tun with minimal/succinct changes?

IF this makes no sense at all, please feel free to pull me up on it