I did pretty much all of the things listed in the guide — disable HDMI output, all LEDs and turn the camera on only when recording or taking the photo. It would still turn off early in the mornings before the sunrise for a few hours so it was definitely drawing a lot more power than was available.

I feel like any charging controller will do as long as it can charge up the battery quickly with the available sun hours. For example, with a 100Wp panel it would be sending 7A at a 14V charging voltage. The choice of your battery and solar panels impacts the charging current so it really depends on the setup.

One great feature is having a 5V USB output directly from controller since that can be used to power the Pi directly.