And online renewals only work when you have the magic cookie they snail mail you. Everything else needs to be mailed in with actual signatures. At least the FAA moved into the 21st century and accept plain paper versions of the forms now rather than their inane carbonless copy versions.
The registration still comes back as a physical card as well. My last airworthiness certificate from the FSDO is a PDF file. I still have to carry the printed version in the plane, but I can make as many "original" copies as I like. At least the FAA didn't watermark "ORIGINAL COPY" on it like the FCC did with my radio licenses (and if you ask for a duplicate they send you one marked DUPLICATE COPY).