Sure you just need a driver with an output voltage higher than the series strings forward voltage rating.
For safety many drivers only go to 48-52V (60V SELV) max DC output.. There are some that go higher.
Hope you realize too that ALL the leds in each string will get the same current so you can't mix 300mA and 750mA (well if you do you should only drive them at 300mA) .. They will all be driven at the same current level.
Assuming most white LEDs are 3.3 volt forward voltage, each string will have a 70 volt drop and 126 watts (3x42) on a 150x200 mm plate? Fire? It is possible.
Note that fire is possible from poorly designed electronics and circuitboard but, instead, from radient energy. LED flashlights of 30 watts and more can heat place paper or electrical tape to combustion (depending on focal length and distance).