My dictionaries list both genug and genügend as "sufficient, enough, etc."
Are there any differences between the two other than one functions as a participle of genügen?
Additionally, are these two interchangeable?
Broadly speaking, both words can be used as adjective but only genug can be used as adverb. Sharing their meaning and being interchangeable, they mean ausreichend, or hinreichend and can be translated with sufficient and enough.
I'd say that you can replace genügend with genug (almost) always but not vice versa. I think there's a slight tendency to use genügend when referring to an uncountable noun while people rather use genug when it's countable.
You cannot use genügend as adverb.
You can place genug before and after a noun but genügend must precede the noun.
When you search the Internet you will find some notes that genug is a particle (namely Gradpartikel) and it's also used as indefinite pronoun (like some, many etc.).
Semantically speaking, that's correct but this is a finer point of language analyzing and does not help you to fully understand its usage at all.