Lol. In what world do you live on that 2.56 umol/joule at the board level, or 2.36 umol/joule after driver losses is "ineffecient these days".
12-15 vero 29s would cost substantially more than my build. A single vero 29 gen 7 cob is $25. Plus another $10-20 for a heatsink. Making for $35-45 per COB. My strips cost $14 each, and the heatsinks costed me $3 each. For $17 per strip.
Yeah it is inefficient by today's standards. I haven't run anything in flower less than 3 ppf/J for more than 2 years now. Plus I have the proper tools to verify which makes all the difference in the world.
As for crying about the upfront cost, boo hoo. You don't need bulky heat sinks when simple aluminum sheet will do just fine. Bridgelux CoBs are far superior to other CoBs as it pertains to thermal transfer which is what makes them so good to use. If cost of light was such a big deal then the best option would be to buy a19/e27 bulbs on sale at big box stores.
For the cost of assembled DIY based offerings you can double the amount of cobs by buying from an electronics supplier if cost is an issue. You can save even more by going with drivers other than meanwell that perform just as well. Doing your homework will be the biggest cost savings.
Then you have those of us who aren't concerned about the upfront costs and just want the best. It gives us the advantage for these kind of debates because we don't have such limitations that require other components, like heat sinks, which further chew into the cost. And we know better to spend the money on the proper tools for measuring what actually matters. QBs, strips and other gimmicks will never be able to compete with CoBs on LES density which means less options over all.
Summarily, no matter what kind of performance you can get out of QB or strips they will always be able to be out done by CoBs for any given space. Want to upgrade? Just add more CoBs in parallel. You will run out of space far faster with QB/strips than CoBs.