the buckets are fine to use. that all i use myself. they are common in the food industry and used for all sorts.
personally i would not bother putting an air lock on it, just use open top style. but then again i would only use it for a fermenter, not for storage. the plastic is not really suitable for long term storage so not good to use as a carboy.
by not putting an air lock on you can use it for other things later.