oregon white oak

In 2014 I bought a 1-gallon seedling Quercus garryana from a local retail nursery for about $15. Here it is in 2015 in a 3-gal clay pot: I decided to grow out a second main trunk line and work on a natural looking informal broom style This tree is inspiring So I grew it out in full sun...

I have a batch of yearling oaks (Oregon White Oak/Q. Garryana) that I grew from locally-collected acorns, with the aim of bonsaiing the most promising. However, I'm a n00b, and can't find info on how to proceed. Should I be letting them grow on unchecked to gain trunk width? Pinching them back...