I think the first two are important, you can choose one from the last three. Personally, I don't think references written by Chinese (big names or with networks are excluded) can make a difference.
找熟悉点的老师写推荐信会好写些。。其他不熟的。。又不是有connection的老师基本可以不用找了。。。不必纠结太多在这上面 因为感觉各种排列组合出来区别都不大。。。out of office不用担心。。。admission committee基本上不会注意到。。。推荐信内容和申请方向不一致也没关系的。。。