Map to Flexfield option in Talent Profile Upgrade

Summary

What has been your experience with "Map to Flexfield" while upgrading Talent Profile?

Content

Is it better to map Custom attributes in Person Profile to fields within Delivered Templates or Map to Flexfield? 

Do we just select "Map to Flexfield" attribute for custom attributes that cannot be mapped to existing attributes within delivered templates?

Are the Flexfields created automatically? Can they be configured for display  - Summary Vs Detail, Labels etc.