green isnt amazing? Without
tarmogoyf 
i dont know what else would be included into g/u builds. The good thing about modern is that it is a new meta and many new decks can be created. This results in (if you have ever looked at ptq results) in a wider variety of contest winning decks. At one tournament you may see an exarch twin deck take 1st 4th and 8th but then in another exarch twin may not even make it to top 8. If you want to try to make your own deck with components not usually seen than you may have an advantage over unprepared metas.
As for your card choice i dont know how to keep the creatures in check. The only way i could think is to use token generators and then have buff spells put on your opponents creatures which green is chalk full of.
Right now the competitive decks that are on the top of my head are: exarch twin combo, abuzing
splinter twin 
and similar copy effects to make copys of creature untappers and swing ftw with a lot of creatures and such. Another deck is red/ blue storm using the usual storm strategy to create a twenty damage
grapeshot 
or
empty the warrens 
. Another underated combo deck is eggs, a really hard deck to play but has a pretty consistant combo.
Pyromancer ascension 
decks are also pretty good. Affinity is an easy deck to start on also and the cards are pretty easy to come by. Mono blue infect has seen some results with
blazing shoal 
removing a
progenitus 
from their hand to pump a
blighted agent 
and swing for 11 infect.
