Comic dubs can be popular, especially if the voice acting is top-notch and the adaptation is well-done. But there are also cases where they don't gain much traction if the quality isn't up to par.
It's not too complicated. First, you need a good recording app on your tablet. Then, find a quiet place to record your voice clearly. Make sure you have practiced the lines and have a good understanding of the comic's mood.
To make comic dubs well, first, study the comic thoroughly to get the tone and emotions right. Then, practice your voice acting to match the characters. Also, pay attention to the audio quality by using decent microphones and editing software.
No. The Undertale community is mainly about positive things like friendship and hope. Abuse of any character, especially in a fanfiction, goes against the values of the community.
One interesting story could be about the characters' reactions to different timelines. For example, Sans might react in a unique way when faced with a timeline where everyone is overly aggressive. Another could be the reactions of the monsters to human technology that they've never seen before, like a smartphone. And there could also be stories about how the characters react to fan - made scenarios, such as a 'what if' situation where Asriel didn't turn into Flowey.