No link, but old soil should be moist so that it stays together. No worries on the new stuff, just water with plain water after transplant. Dark period after if possible for the shock, not enough to trigger flower (less than 8 hours) if veg period is to continue. Raise the lights for a few days, to reduce heat and intensity, aim for warmer light (red light, lower Kelvin value) to encourage new root growth for transplants for at least a few days, and most importantly, be gentle, dont overly compress or depress the new medium, and look into adding beneficial bacteria and fungi for root development, specifically azos and a wide range of mychorizae.
the dark would confuse a little plant.. Just raise your lights to go easy on them..
Stopping photosynthesis is not a way to "go easy" on a plant. Going easy would be giving less lumens, but still letting the damn thing grow.
One dark period of 12 hours will not initiate flowering on a plant.. The hormones need to build up inside the plant.. It takes a few days of consistent 12 hour dark periods to initiate flowering, so don't worry if your plants get a long night here or there.
Do not OVER WATER when you transplant.......it will slow things down.I have stopped watering in my transplants and just soak the new soil first.....roots seem to search and spread faster for me this way.
I usually wait until my plants are dry. Then I get the new pot and add in some moist soil. Take the pot the plant is in, put the stem of your plant between your middle and ring finger (or middle and pointer if you get better control that way). Flip the pot over and give the bottom a little tap until you feel everything slide out. I usually squeeze the bottom of the root ball up to break things up a bit and then flip it over into the new pot. Then you just add soil around the sides and any on top you might have lost in transplanting.
The only time I've had a plant have a bad reaction to transplanting this way was when I didn't let one of my plants dry out all the way and the root ball ripping in half because the wet soil at the bottom stayed in while the dry came out. So make sure your soil is completely dry before you transplant.