Don't pay too much attention to the number of LEDs. The light out put in Lumens needs to be comparable to the 921s you are replacing. I have installed the same type you linked to above. I have done 24, 36, and 48 units, in both normal and warm white. The warm is too yellow in my opinion. Mine came from China, bought on eBay. They are cheap enough you can experiment with different ones to see which suit you the best.
I have not mounted any of mine with the double sided tape. No failures in over 15,000 miles of driving and over 150 nights camped.
2008 Chevy Silverado 2500 Duramax Crewcab
Jeep Commander - sold
Flagstaff V-Lite WRB26