Mr. Wright, good evening to you Sir. Queen rearing is my passion, my eyes still sparkle every time I see a queen hatch. I natural breed, wet graft or instrumental inseminate my queens.
You question regarding royal jelly (RJ) makes me think you correctly learned a well fed queen is superior. Therefore, a queen rearing beek can add RJ and produce better queens... The more food the better, right? The idea has merit however there are concerns you should know about which I will discuss in the next paragraph.
Not all royal jelly is the same. The nurse bees change the chemistry of RJ as the queen ages, prior to capping. Most queens I raise have left over RJ in the queen cell after departure. So the amount of RJ in the queen cell is not a limiting factor. Also there is the issue of adding the RJ to a queen cell without disrupting the breathing holes located on the sides of larva, the entire length of the larva. These are tiny holes and if a larva is rolled, or coated with RJ, the larva will suffocate because it takes time to open and close the breathing tubes.
If you wish to raise the best quality queens then focus on the nurse bees. The nurse bees are the ones needing food as they make the RJ in their head ,, of all places. Yes, in their head. Lots of nurse bees, with frames of pollen and honey then the nurse bees will take the best of care your queens. When I raise queens, I loc up my nurse bees, screened entrance shut, without larva to feed for 24 hours. Then, after 24 hours, I provide the queen larva to the nurse bees while the nurses are all full of RJ and just waiting for a larva to feed.
There are many factors to raising queens inwhich entire books are written. So with this topic, your topic, we are limiting to the subject to royal jelly.
Cheers
Van