Archival framing methods are the way to go, which means 100% kozo paper hinges, 100% cotton rag, acid and lining free, alkaline pH buffered 4-ply mattes, and conservation glass or Plexiglas.
You can also go with plastic corner mounts and hinge the top matte to an acid-free foam core backing with acid free linen hinges.
There is some back and forth on buffered and non-buffered matte board, but with concerns about general acidity of the air, using buffered matte board is the more conservative method.
I have always found Japanese paper hinges (using rice starch paste) a real pain to work with, so I tend to use a middle ground:
- Acid-free linen tape hinges
- 100% cotton rag, acid and lining free, alkaline pH buffered, 4-ply mattes
- Conservation glass or Plexiglas
- Acid-free foam core backing
For something that you want to be long lasting as well as reversible (so the owner can have the print or art re-matted later, etc. if so desired) you will want to avoid dry/cold mount methods. It appears you can use those techniques, but why chance it?
If you insist of entire adhesion to backing for a totally smooth appearance, digital prints should probably not be heat mounted. Ask your framer or reprographics professional. In Pittsburgh, that is Modern Reproductions and Tristate.
Pictureframes.com has a “personal frame shop” on their top header. This is a great way to try on mats and frames and you can even select a wall color behind the framed art. You have to upload an image from your computer. Because color can appear differently on a screen than it does in reality I still suggest using a local framer (in the Pittsburgh area I like Mark Panza in Millvale, PA at Panza Frame and Gallery).
If you decide to have any of my work framed via an online framing business, you must take the dimensions from my actual art once you receive it and not from my “approximate dimensions” listed for each piece.