Whether or not to rack to secondary is entirely up to you and your needs. I sometimes do, if I’m in the middle of a near-constant brewing schedule; I only have space for one 6 gallon primary fermentor, so if I’m brewing a lot (like every-other weekend) I’ll rack to secondary to free up my primary for my next batch, allowing the just-racked batch to continue conditioning in a secondary while I start my next brew. The last batch of Chocolate Milk Stout I brewed was a 3 gallon batch, so it went right into one of my two 5 gallon secondary carboys, where it stayed the entire fermenting, conditioning and “dry hopping” time (with cacao nibs, of course.) Quick turnaround beers like a Cream Ale or English Mild, will only see the primary vessel as well.
For what it’s worth regarding cacao nibs, I start mine soaking in vodka on brew day, using a volume of vodka that is approximately double the cacao nibs volume, in a clean, lidded jar. They will absorb a lot of vodka, so make sure you use plenty. When it comes time to add them to your beer I dump the full volume of vodka into the beer and then spoon the nibs into a sanitized muslin hop bag that is inside the neck of the carboy, using about 5 - 10 sanitized lead-free marbles to weigh down the bag, and sanitized unflavored dental floss to tie off the bag and suspend it into the middle of the beer.