Hi Thunder lol no they won't bite you, they're not as territorial as some other bigger cichlids.
It's a good idea to have two heaters, but not necessary, personally I don't do it and haven't had any problems *touchwood*.
Discus reach adult hood at 18 months, they continue to colour up until then which is awesome, so fun to grow them out from young, which means yes a barebottom (BB) tank and daily, twice daily, every second day water changes, the more the better. You don't "have" to, but they grow much better and don't get stunted if you do. A stunted discus is one with a big eye, it's out of proportion and doesn't look as good as one with a small eye. Overfiltration isn't as good as daily water changes, because filters alone do not remove nitrate. Nitrate (basically fish waste) is believed to be growth inhibiting (hence the need for daily water changes to remove nitrate).
Real plants are best because they help remove bad toxins from the water, like ammonia and nitrate. Discus prefer more driftwood than rocks or plants, because this resembles their natural habitat more realistically. The odd rock is found in the wild however.
A BB tank doesn't look as nice as a planted, but I have found the best of both worlds by weighing some normal plants down in a BB tank. It's easy to clean AND looks great. I will post some pics when I get my camera arriving soon to show you what I mean.
HTH