"Is an Orthodox Christian obliged to follow all that the Church teaches, or is there some leeway that is left to individual choice?"
If the Church clearly teaches something, then an Orthodox Christian that wishes to go to heaven should endeavor to embrace that teaching and obey it with all their heart and soul.
Christ taught us:
"He that heareth you heareth me; and he that despiseth you despiseth me; and he that despiseth me despiseth him that sent me" (Luke 10:16).And so obedience to the Church is the equivalent of obedience to Christ. And so, for example, when the Scriptures, as understood and explained by the Church, teach us us that something is either forbidden or obligatory, that should settle the matter.
Further, the Seventh Ecumenical Council declared:
"If anyone breaks any ecclesiastical tradition, written or unwritten, let him be anathema."But of course this applies to what the Church actually does teach. When it comes to matters that are debatable, to the extent that the debate has any real merit, there could be room for reasonable disagreement. So if there is a question about what the Church teaches, it needs to be examined on its own merits. However, often people try to raise questions about matters that there really is no question about, and so if you catch yourself grasping at straws in attempt to find a justification to ignore something that you know the Church really does teach, you should know that we ultimately will have to give an account to the God who knows whether or not we are just making excuses because we don't what to hear the Church.