I went with backgrounds, inspiration, and advantage disadvantage.
I didn't choose old school feel, because using DMG variants and Unearthed Arcana variants I recreated the feel of how friends and I played during 1e and 2e (including tailoring the barbarian to be much closer to the 1e version)
I didn't choose Rulings not rules/DM empowerment. With regards to rulings not rules, that is how I ran 3e. For instance, in one of the early 3e issues of Dragon, Tweet and Reynolds discussed the philosophy behind the 3e skill system including "the commoner standard", and what Easy, Difficult, etc. meant. I just used that article and the 3.0 DMG "DMs Best Friend" with modifiers ranging from 0 to 20 and ignored all of the sample skill DCs in the PHB. I also don't use many non-core combat feats that I felt anyone should be able to do (e.g., the one about throwing sand in the eyes). As for DM empowerment, anyone reading the 3.0 DMG knows it is stressed several times- many DMs did not read it or ignored it.