I am pretty sure that 12W TMC 400 will be more than enough for any 30 cube nano or even something larger based on my DIY LED output.
These Osram LED's come in 2 setups 80 Degree beam and 150 degree beam angles. Now I am almost 100% sure they would not give 150 degree beam LED inside as that would render them useless. At 80 Degree beam angle you get fantastic penetration and spread for your nano. On other hand 80 degree beam angles are more useful for deeper tanks than 30cm 35cm deep cubes. My guess is it can penetrate easy to 45cm deep tanks. But don't get me wrong this will give plenty light with pefrect spread for any nano's out there we use.
Now I can only guess PAR output but at the substrate of 30cm cube it could be around PAR 100-120 which is plenty for planted tank. I grow my plants at 45-55 at substrate level without problem (except glosso
).