For this question, I mean 結構 in the sense of 'no thanks.'
So if I were to say 結構です informally, it would be 結構. And if I wanted to sound more strong about it, I would add もう in front of 結構 so it'd be もう結構? But is there other ways to say this, maybe more gentler? Perhaps like:すみませんがもう結構です or ごめんがもう結構?
And for 結構, is there any restrictions on how I use it? Like I can use it to refuse food or drinks, but is there anything that I can't use it to refuse?
Thanks so much in advance, and if I need to further clarify anything, please let me know.