Questions about COBs and power supplies from a beginner
These COBs (and most of them) are current-driven, which means you need a current driver, not a voltage source.
It also means that you cannot connect them in parallel. You could if by adding some small resistor in series to each COB to compensate for the voltage differential, but it is not very safe and they may end up dying after some time.
In your situation, the best two options are to connect them in series and have a current source that has a voltage high enough to drive them or use an independent driver for each.
Note that if you are going to drive them at 70W, you need to have some good cooling, otherwise you will kill them.