I'm playing paper magic for a while now. When playing modern I always fall back to taxes. Considering my strategy and the choices you have to make death and taxes, green white is my favorite one. I only have 2 modern decks, so when choosing to go to a tournament I choose this one because of the diversity in games. My other modern deck is a ur storm deck.
I've posted here to help me when I need a deck list. But you are all free to post your (dis)likes. It can only make it better.
First try to disrupt your opponent's game plan with cards as Leonin Arbiter or Thalia.
Then try to make a clock with bigger creatures as Thought-Knot Seer or Reality Smasher.
Simple enough game plan isn't it?
Then the sideboarding:
Ethersworn Canonist
Good against combo decks or other decks that try to cast multiple cards in a single turn (Enchantress, Storm, Ad Nauseam,...)
Felidar Cub
Mainly a card you need for answering Blood Moon. So whenever you play against a red deck that may cast Blood Moon, it's an auto include (Burn, Enchantress, Bogles,...).
Knight of Autumn
Enchantments and artifacts are finding there way to modern easily. This gives a great advantage to decks that play these cards. In average I like to play these when they play enchantments or artifacts. Not like Felidar Cub, only against Blood Moon, but when it has more than one target in average. (Tron, Enchantress, Bogles,...).
Sanctifier en-Vec
This is a card I would suggest playing against everything playing black or red. This creature has protection from these colors. The second ability makes this card even better, Rest in Peace for all black and red cards. (Death's Shadow, Jund,
4/5c Good Stuff,...).
Collector Ouphe
F*** you artifacts (Tron, Affinity, Heliod Life,...).
Thrun, the Last Troll
Every deck that wants to control or destroy everything you have, has a hard time dealing with this card. (Jund, control, Junk,...).
Dusk // Dawn and Settle the Wreckage
These cards do basically the same. Sometimes they both are great, sometimes only one of them. Depending on the match-up, if a board whipe is necessary I consider one of those cards (Zoo, Tribal, 4/5c Good Stuff,...)