でわ is an incorrect form (it's written
In terms of nuance,
じゃあ are very colloquial (whereas
では is not).
じゃ is a bit more "light" IMO. As in, it can just be a filler. For example,
じゃ、バイバイ！ just means "Right, bye!".
じゃあ means it has real semantic meaning - for example,
じゃあ、バイバイ！ means "In that case, bye!". For example it can express annoyance (
え、持ってきてくれなかったの？じゃあバイバイ！), or emphasize you are doing something because of something (
え、いらないの？じゃあ、もう一つ食べようかな (otherwise I wouldn't have)).
They are really close in meaning though (e.g. it'd be the same meaning if you said
では is more formal (e.g.
では、さようなら), and it would be odd to use it in a colloquial way (for example, it's slightly odd to say
では、バイバイ！). In terms of meaning it's closer to
じゃ (as opposed to
All three have very similar meanings though.