Yes, you can overfeed the fry with BBS or any food for that matter-By overfeeding, sometimes you can see buoyancy problems that may or may not resolve on its own. In some cases overfeeding can cause long term problems with developing fry.
A good varied diet fed in small frequent meals is best-Watch their tummy-it should look round and usually will be the color of the food.
I would make water changes after overfeeding and if you add some common snails to the fry tank-they can help to a degree with cleanup between the needed daily water changes.
IMO/E-adding live plants is almost always beneficial....Live plants provide-cover, resting spots off the floor, help with water quality and provide some microorganisms for free range fry food-This of course can vary.....
Water changes are also really important for best growth/development-When spawning using the standard method-at least 50-80% daily to twice-three times a day-depending on spawn size and if you have lots of fast growing/thriving plants-again, many variables....
Proper water temp-neither too warm or too cool-I have found more with developing eggs than fry-that too warm or cool can cause too fast or slow development that can result in weak fry.
Heat and humidity over the water is also important-especially when the fry start to develop the labyrinth organ-between the age of 2-6 weeks. Too cool/dry air over the water when the fry take their first breath of atmospheric air can sometimes result in mass die off and/or long term health issues.