Designing brake light with specific luminous intensity
Firstly, power LEDs are bound to be driven by a constant current source. Direct parallation of LEDs is also a bad idea. Unless you fit each LED with a CC driver or resistor (when using a resistor you should limit the current well under maxim) It's better to put some in series. The chance of led failure is extremely low if you drive them correctly. In a series connection every member of the circuit gets the same current and it eases the voltage difference as seen by a switchmode driver. You can use a hysterisis mode current driver designed specifically for LEDs.

Modulate the LED brightness by applying PWM >4KHz through chip control or adjust current feedback in some way. Use powerful LEDs more powerful than you need so that you can tune the brightness.

LED chips are usually very broad by default. Some types are pre fitted with lens so they are narrower. If you have specific regulations requireing specific brightness or specific angle, please let us know.

EDIT: Having viewed the 2 links provided by you I think they are 10mm LEDs.
https://cdn.solarbotics.com/products/photos/e8bdbcc82c6ba23a4476b929e30dd0c4/ubled10-img_0116.JPG

Oh another thing. If you decide to use a resistor approach your drive voltage should be by some order higher than the LED Vf. Say if your LED Vf is 2.3V, do not drive from 2.5, 3V, 3.3V source. Drive from 5V or higher through a resistor instead. This is because modern LEDs are sensitive to minute changes as a result your light may flicker if your drive volt is too close.