It is safe to wear a wig after transplant. You ned to wait until you are completely healed. It is usually safe to wait for a few weeks and check with your doctor first.
Yes, you can wear a wig but you must use attachments that fix the wig to the longer hairs or just no fixation with it. The key is not to use glues and to make sure that the wig does not rub against your FUE recipient sites.