Wish

I'm sure this has been discussed before but I'm still a little confused about how Wish works.

Is it only affected by your wisdom score or does intelligence factor in as well?

Is there a benefit to having 21 Wisdom or is 18 good enough.

Basically, I'm about to roll a Dragon Disciple and I'm wondering if I need 18 in Wisdom and Intelligence by the end of BGEE.

Thanks!