First off, transhumanism is an ideology, not a state of being. You can be a transhumanist and have received no modifications at all.
Shoving mechanical bits into yourself doesn't really qualify you as a transhuman anything.
To be genuinely transhuman, your alterations have to be part of you, otherwise you're just a dude in a suit or with stuff shoved under your skin. Genetic modification is the obvious choice, although certain kinds of surgery, including LASIK, hip replacement, and artificial hearts, are arguable. Because of the way it interacts with her sense of touch, Zoe Quinn's magnet under her finger is probably the tiniest thing that can be remotely qualified as an upgrade.
Yes, your grandma with a titanium hip and tooth implants is more transhuman than the guy who stitched a thermometer under his flesh.