Well due to the fact that I grow under lights and summer most plants out doors, there are only so many orchids that I can grow. Therefore I stick to smaller growing orchids for he most part. I have tried Rothchild types, I have tried Phrags but for my conditions, I grow mainly Brachypetalum species and hybrids. I do well with Paphiopedilum sukhakulii, coloratum type things, and a few others. Most do very well under my lights. If you research the Brachypetalum group there are several species listed, of those, I mentioned the ones that seem to do better for me.
Just recently I am trying a few clones of P. armeniacum and P. micranthum. I have only had those for a couple of months ,way too short to have any opinion about them under lights. But that is what orchid growing is like. You can get caught in a trap where you want to try everything that you see. But that has limited rewards. You really need to take a few years to understand what type of conditions that you can provide and select plants for those conditions. Your success rate will be much higher that way. You do not buy cool growing orchids unless you can provide the "cool"!
Growth rates for everybody's Slippers are different. Some people grow them all well while some people can't grow them at all. It takes experience to recognize which is which.
Now when it comes to fertilizers, it depends again on what you grow and where you grow them. But for the last 9, maybe 10 years, my plants in general are not doing as well as they have. In the past, I have noticed that orchids in my care have done that before. It is like they get tired of the same old fertilizer. If I switch up fertilizers, the plants respond with better growth and more flowers. But this is just seemingly what noticed with my plants. But I am going to make a change real soon. I am going to switch over to First Ray's fertilizers, both the k-lite and kelpak. One is a fertilizer, the other a tonic of sorts. But I will order that after Labor Day. I am in the midst of planning a trip out to the Dakotas with my son around Labor Day. We are going to the Badlands, Custer State Park, Needles Highway, Sylvan Lake, Devil's Tower and Mount Rushmore.