I guess you realise this will be 10A of current combined can the electrics handle this? At this sort of current you will be wasting quite a bit of combined power in the resistors. You would be better off using a dedicated LED driver so the brightness is maintained even when the engine is idling. Worst thing I can think off is LEDs that keep changing their brightness dependant on engine revs.
If you are attempting to put out a lot of brightness like the example.. I would urge you to build or buy an LED driver.
Remember the calculation you did above with the 5 Watt resistor?
That is 5Watts wasted as heat, and nothing more... And each string you put in parallel will add to this...
An LED driver will be much much more efficient, and will allow you to run more LEDs with less current.
I have a couple 10Watt White LEDs at home with a driver that work on 12V. They are bright.. like a single 10Watt LED outshines a 60 soft white incandescent.
The picture you provided is kind of hard to tell how bright they are in reality... the exposure settings and the brightness outside could both affect the reality of the LEDs
900mA to 1000mA is not a huge difference. The driver I linked is for a Cree 10W LED.
You are right in your assumption of needing 5 drivers for 5 LEDs.
The only way around that is to get creative...
A boost converter will bump the voltage from 12V to say... 60
From there, you would need a 'constant current' regulator. (Buck, or linear type)
You will need to manually set it to 900-1000mA, but you can then use that to run 5 of those LEDs in series.
The other alternative is to get lucky and find a constant current boost converter that you can manually adjust for 900-1000mA. This can be purchased or built.
The other keywords here for you to search is 'constant current', 'boost converter', 'adjustable'.
I don't have an example product unfortunately for you. I have been lazily looking for one myself that can run 80 - 100W of LEDs. . . I may end up just trying to build one myself