If you are off the title, your fiance will own that home outright and that asset will also not be in your name. You can still have that asset in your name and not be on the loan. This will give you advantages when/if you want to refi out of that loan or get a HELOC, you have the right to use the equity.
In those situations its best to talk to your fiance, and in my experience its better to be on the title if you are paying some/all/a little of the mortgage, taxes, doing work on the property etc..just to protect yourself if anything (god forbid) goes wrong with the relationship.
When you are ready to purchase another property and you are able to purchase on your own, you still will not be on this loan, just on title. Moving into a home with ANYONE and you are paying for anything associated with the property, in a relationship (especially fiance) I would get on title.
This would not effect you purchasing another home as far as DTI is concerned in the future, only secure that asset in your name as well as your husbands/fiance.