Choose the tier you want and back at that tier. Then add on the correct amount of money to include the Add-On that you want. After the campaign we will have a pledge manager to help sort out what you are getting.
Yes, you can back at $1 and upgrade later. It is better for stretch goals etc. if people pledge during the campaign so we can plan but do what you can. It is possible that some add-ons will increase in price. The pledge manager will be open for at least 60 days.