Grey Wolves and NYGM Tonnage War are two seperate 'mega-mods'.
Many people wanted the features offered by both, so you can combine them. Some people only wanted the compaign changes, but wanted to play with the 'rules' of one mod or the other.
Thanks to Rubini all of this is possible.
You can play GW with the unified campaign.
You can play NYGM TW with the unified campaign.
or
You can combine GW and NYGM (by installing GW,then layering NYGM over top.) and then play the UC. So you would be playing GW with a tonnage based reward system with all the new campaign changes. (new cities, unit patrol routes, air cover, etc.)
Instructions here:
http://www.subsim.com/phpBB/viewtopic.php?t=50377