I know I was late to the Taiwanese Gaoshan party, but let me just say I am glad I found my way there eventually. While I have not fully explored Chinese Tie Guan Yin either, and the Gaoshan is different than the best Tie Guan Yin I have had, I feel these green oolongs have certain incredibly obvious traits which show if they are or are not high quality/ fresh.
For the longest time I stayed away from these greener oolongs as I felt they offered up a slight hint of bitterness, that was incredibly out of balance compared to their otherwise lighter honey, butter and floral flavors. But when you find a green oolong that avoids that bitterness they can be absolutely sublime.
Having delt with a decent bit of those slightly bitter green oolongs in the past, I realized they can often be pretty darn tasty when brewed almost western style. I have consumed quite a bit of those bitter green oolongs with 6-7 grams (one packet if it comes in little individual serving packets) for 11-12 ounces of water, and get several nice steeps out of them.
For the good stuff though it is gaiwan all the way, I am toying with the idea of a Yixing but not entirely sure yet. The hardest part for me with brewing these Gaoshans is not adding too much leaf. that thin layer on the bottom doesnt look like much until the 3rd or 4th brew when its packing your entire gaiwan.