Question and Answers setup
Your Option 1 and Option 2 seem to both implement "answers" as comments...

Another option (= Option 3) would be to implement Answers as another content type, combined with an entity reference field (multiple values allowed) added to your Questions content type.

By using a content type for both Questions and Answers, it would probaby simplify anything about voting (either Question or Answers), and you could also use the Flag module (e.g. to mark "an" answer as the "accepted" answer).

At this time it's too early (= not ready for D8 yet) for some typical other modules that could be added to this later on:


the Rules module, to implement whatever logic you'd want (eg: only question authors can flag one, and only one. answer with the fag to mark an answer as accepted.
the Userpoints module, to implement your reputation system.


PS: you probaby have a good reason why it has to be implemented in D8, but if D7 would be "good enough" (at least for now), you could implement something similar to this Option 3 by using what is explained in this answer to "How to implement a reputation based system with badges in Drupal similar to StackExchange sites?".