You know im really curious how those bubbles who have "hearts" and "~" would sound in real...

Now that you say it... (⊙_⊙ )

I think it's more of a tone of the voice, so it would probably sound sweet(?) or when you say something cutely maybe

As far as i know, "hearts" in bubbles would be in flirty tone (ie. darling ♡ )and the "~" depends on context it can be singing or just saying the word longer (ie. hero~ --- herooo or lyrics like "and now they know~~)