So, I have 2 sure fire 6p's and what seems to be a longer version of a sure fire g2. I'm building my go to dream AR. And of these three, which should I put on and what upgrades to the lights should I make? Or I can take the TLR-S 1 off my HD pistol and put it on my rifle which I wouldn't prefer but I can do.

I guess just pick whichever one you like best and use it.  

I'm a pretty big fan of the new P2X Fury Tacticals.  600 lumens and clicky tailcap.

Where to get these though? BCM has been out  of stock for weeks[s]

disregard, I should make my own post.
However I second the Makoff suggestion, their stuff is gtg

If you want to use one of your existing lights then the biggest upgrade would be to swap out the bulb in one of your 6P lights for an LED - Malkoff is the most commonly recommended for weapon usage (and for good reason.) If you want to upgrade beyond that there are literally hundreds of options depending on your budget and needs.

See that's what I've seen. It will be a home defense/shtf/hog hunting rifle. I think I'll buy an offset mount and the LED. Where can I buy one? And do you know if they make a tail click on/off button? I'd like to spend about $50-$75 on upgrades (not counting the mount) for the light but if there is a better choice for the same I'd be happy and get it.

Go to Malkoffdevices.com, and buy one of their p60 LED drop ins.  Then you just spin the head off the light and swap out the incan bulb for the LED.  Out put will be much better and you will have a solid light that will last forever and have a way more output than the incan bulb.  Its easy and doesn't involve buying another light.  If you still would rather buy another light, go get a Surefire G2X or 6PX in the single mode.  Dual mod lights suck on guns.  They are usually $50-60 on the G2X and $65-85 on the 6PX.  But really, no matter what, if you have 2 6P's sitting around I would swap them to LED anyway.  Makes for a much more useful light.  I have 3 of them and I just have 1 more to get swapped out.  The 2 with the LED's in them are currently sitting on guns.  While the third (and incan bulbed light) is sitting on my desk.

You could always go TLR-1HP

That bezel gives that light one hell of a throw lol

 
I have this light and will highly agree with how great it is. The throw is ridiculous due to its 46,000 candela, but at the same time can serve very well indoors without self-blinding because it only has 200 lumins. Unfortunately, Streamlight has replaced this model with the TLR:1-HPL which is a combination of the long-throw and high-lumin models. It now has 48,000 candela and 630? lumins, so the battery life will be a bit less and it has a huge flood effect.