Design considerations for LED strip PWM dimming
Design choices that need to be put into your design spec;


Supply choices


current, voltage drop, cost
custom LED driver supplies cost about the same per unit watt so a higher voltage like 24V to reduce cost of copper in the flex circuit in conduction losses in each path and common return or even higher if more than 1 Amp per port from using 12V. In Japan it is common to see circa 100Vdc supplies to drive LED COBs with low voltage low side drivers with regulated current and PWM with an LC filter.
ATX supplies are cheap with $0.15/W with the 12V portion of the PSU this is less than the cost of the LEDs per Watt but a significant part. Don't compromise reliability here.
CC limited supplies for each port are best so that current is regulated while Vf variation can be 10% at the same current. This can be done with current sense feedback.
dimmer control interface
Many options by design can be chosen including I2S, uC PWM , RS-485 digital control to DAC  or 0 to 10V control interface for analog control. This depends on User interface requirements for remote control. 

Environmental protection: IPxy x from objects, y for water


IP20 (basic finger size protection)
IP54 (limited protection to dust and water splashes)
IP65 ( full dust protection and low pressure water )
IP68 ( full dust protection and water immersion 1m+ )

EOS protection


induced stray lightning for outdoor use
handling protection from ESD during assembly
this is more necessary when the LEDs are OFF when high impedance and susceptible to induced negative fields or discharges on long cables or contacts.  It is only most sensitive to negative voltages below -5V to damage or -15V if a string of 3 LEDs.
the best way to protect LED's is a reverse biased diode between driver and switched rail. Risk depends on exposure and frequency of lightning strikes per year.  this also prevents the potential 

Beware of Luminous intensity and quality of supplier specs.


Watts don't always translate into accurate colours as there can be an order of magnitude difference in red &amp; blue power LED which tend to be more expensive and lower efficacy in combo LEDs and also more expensive to combine 3 different chemistries into one epitaxial chip.  Choose reputable datasheets from brand name sources like Cree or those from Japan, TW or Korea and compare.
for a good tool, buy a CIE corrected luminous intensity meter >$50 or for $5 buy a Panasonic CIE corrected 5mm Photo Sensor and operate using 5V from a 9V battery with an LDO into a gain load resistor into a cheap DMM with a diffused >1cm area to capture the LED light for testing.
also consider that color temp will change with aging as each LED may degrade at different rates according to operating temperature and duration used. LM70 is the standard used for White LED's but RGB LEDs have the same issue. Often the phosphor ages slightly more on white LEDs so we call this a small rise in CCT or blue shift.





As far as brightness perception, our eyes have a very wide dynamic range yet TV images are limited to about 2 decades of range.  It would be very hard to recognize a 30% loss in visual power from time to time as our eyes and continually adjust and you need a reference for comparison. Yet small changes in LEDs side by side with variations of different wavelengths or intensities are easily seen on big screen LED billboards due to close proximity.  So in short recognize differences far easier than absolute values.  This is often due to cost vs bin size specifications of supplier choices.  a 3:1 range of LED intensities can easily exist in open production but a 10% single bin quality exists at a premium, so supplier selection and specifications depend greatly on the application and ability to recognize differences.  If you were driving in a tunnel of LED with a string of LEDs along the road and you paid a lot for this installed, you might be critical of the supplier if some seemed off-colour or insufficient intensity.  ( I had a customer like this and very few complaints in a million LEDs over 10 years with most of them in 1 Cd/mA range at 20~30 deg.)