A good sequel expands on the original along many axes. It's more extreme (which is particularly in the case of horror), it adds depth to the world and finally it derives a more complicated plot on the foundations set before it.
On these measures, Smile 2 is a great sequel. It is of course more of the same, but it's more creepy, polished and deep than the first, although this may come at a cost to its authenticity... but only if you're really paying attention.
The biggest flaw is also carried over from the first movie - at over 2 hours it's too long for a horror movie and the otherwise excellent set pieces suffer for it as they're diluted down.
Overall though Smile 2 gives a fair whack and just about gets a recommendation.