I use Fluval lights on all my tanks. I have two of the 2.0s running right now. The main difference I can see between the 2.0 and the 3.0 is that the 3.0 has a manual off/on switch whilst the 2.0 can only be controlled via the Bluetooth app.
The high-tech tank I'm running with the Fluval 2.0 is 60x30x30cm, I have a Monte Carlo carpet in it which is not spreading quite as fast as I'd like, but I don't think the light is to blame- I've crystal shrimp in there so can't use EI dosing. The second tank with a 2.0 is a low-tech, low-light jungle tank. I've never turned the light up to 100% on that one.
I am not sure the 2.0 would be strong enough for a tank that is 45cm deep. I can't say for certain, however, as I've never tried it. I don't know if the 3.0 is stronger.
I'm also not sure if the 3.0 is worth the price difference as I just bought matching 2.0s because I am quite happy to use the app to control. There is one drawback to the 2.0- if there's a power cut, the light thinks it's midnight when the power comes back, which could be a serious problem with a high-tech tank if you aren't around to reset it using the app.