質問: is it 元気な 人です or just 元気 人です?
回答: 元気な 人 ← correct. (adjective)(noun) 元気(genki) 人(hito) ← wrong. (noun) (noun) 元気人(genki jin/bito) ← as a slang or a unique noun, it's okay. actually, according to some dictionaries or a grammar site, 元気 is a noun/an adjective verb(形容動詞)/an adjective, but 元気 is a noun, 元気だ is a 形容動詞, "元気 itself is an adjective" is wrong information.