Congratulations on grafting and cell building so that it WORKS!
I am of the opinion that the grafting is the easy part. The hard part is the planning. Both planning pre-grafting to get the cell builder to work out, and post-grafting so your resources are put to their best effect.
I use 3 frame mating nucs - a deep that I slotted, put 1/4 ply dividers in, made 3 plywood inner covers for each apartment. Betterbee sells them for $50, if that is of interest.
If you make your own 3-way mating nuc, be advised that you will benefit by having the entrances be hard to confuse when seen by a nearsighted person from a distance.

Bees actually have poor detail vision, a bit like a nearsighted person, and the queen is viewing the hive as she returns, from a distance. You can site each mating box facing all points of the compass, or alternate front-back, or put chairs or other large items next to some boxes - but if 3 identical entrances are side-by-side for each 3 way mating nuc, then she may have a problem.
I drilled holes for my entrances, so I could cheap out and attach a fixed bottom. The middle one is on top. The 2 side ones have different shapes painted above each, and they are near the bottom of the box. We went with a 3" dark circle for one, and a 4x1" yellow bar for the other. For one style. The other had a 4" strip of electrical tape upright, and a 3" strip of gray duct tape horizontal. I had 2 boxes (each style) with 3 of 3 queens come back mated.
Be very very careful that the 3 apartments are bee-tight.
And you can just pinch or chuck the queen cells you cannot home. A queen cell is a very different investment than a mated laying queen, from the beeks' point of view and the bees'!