Been there, done that, matrix, project-aligned, IPT, etc. The big problem with matrix is that the functional managers don't really work for the PM, so there's not as much accountability for everything, technical, schedule, and cost.
I would dispute the notion that a PM can be completely untechnical. That can only work if the engineering manager is absolutely onboard with the PM, otherwise, a litany of minor overruns on minor tasks results in the "Costco Effect," lots of little things adding up to a big bill.
TTFN
FAQ731-376