For my taste (sour-head) adding everything in primary is the only way I've gotten the sourness of something like a Russian River or Cantillon beer. With barrels it is much easier to get a beer to sour after a clean primary fermentation, not sure if it is the oxygen, the wood, temperature stability or what... If you want a mild tartness, you can do a clean primary fermentation, and pitch the bugs in secondary.
I rack to secondary after 2-3 weeks, never had an issue. Beer starts looking "clear" when it still has something like 100,000 cells per ml, and trust me your beer won’t look clear that young. So, no worries about leaving the bugs behind. I do leave my Lambics in primary for 12-15 months, it gives a funkier more rustic character (but not more sourness) that I don’t like all the time.