No, it's not good or bad. You just prefer one thing over the other. I don't think it would hurt to let the next girl know, not like "I don't like thongs." But "babe I think you'd look really sexy in these". Just think about the approach.
Of course not, I personally don't find thongs attractive either. Everyone has a personal preference, and you just happen to dislike thongs. Tell your current/future girlfriends what you're into and hope they wear that for you instead
No. I don't think thongs are sexy either but I wear them often just because I often wear tight clothes and I hate panty lines. I think bums look better in cheekies anyway. Thongs really don't do good butts justice.