I am not the most experienced on growing orchids in S/H but since I grew about 90% of my almost 200 orchids in S/H I can tell you what I observed: roots after transfer in S/H behave differently for every kind of orchid. Also I only use transparent containers for every kind of orchid, so I can check on roots, and my containers have holes in the bottom and side of the pot. I fill the pot with LECA pebbles and than the potted plants are placed in large trays with elevated margins or smaller box like containers if they are to be hanged on the wall. The level of liquid in the trays is about 1.5- 2 cm. I had 0 success using single pots with holes on the side, where the liquid stays in the bottom part. In my opinion the liquid with the nutrient has to be able to circulate.
With the phals I trasfer them in the pebbles, leave them in their old place and watter them normally with hydroponic nutrients- so I grow them first for a month or so in inert media, after that they go in the tray with lower levels of liquid for a month or so, and if everything seems ok, after this period I move them with the rest of the phals. I transfer in S/H only if the weather is very warm and after cutting the flower stems. This way I can reduce root rot to minimum. With the cattleyas I do much the same, of course they need more light and stay outside, the same goes for the cymbs and oncidium types. I have 0 succes in growing Miltoniopsis and Buragearas in normal growth media or S/H so no advice about them too offer.
The paphs I transfer immediately in the tray with liquid after repotting, they seem to like it and do not rot.
Since the pots I use are are food containers of about 1l, about 18 cm tall (no S/H pots available here or if they are are too expensive), every 2 weeks for the phals and 1 week for the rest of the orchids I watter every plant from above with 30-40 ml of watter with nutrients. Cymbs get more watter, smaller plants of course get smaller containers, and lower levels of liquid. The keikis I plant directly from the mother plant in pebbles and follow the same rule from above, a month watter as if in normal media, then less liquid and so on.
I always keep an eye on the temperature. In cooler periods I lower the levels of the liquid, to the point of keeping the pebbles moist with only a film of watter in the bottom of the tray.
I have no problem with the green algae forming in the pots, they do not smell nor seem to bother the plant.