I also did this trip over the summer. Left Roche Harbor with the form to get
the annual customs decal ($25), filled it in when I returned. Had no I-68 or
CanPass. Checked in at Bedwell by phone at the customs dock. Declared some
wine and beer and no charge was applied (probably would be if you're in a
floating bar).

Checked back in at the dock at Roche Harbor, painless and courteous
experience as it was in Canada (handed over the form and $25 and received
the decal in the mail a week later).

I like Roche Harbor, great place for people and boat watching and has a good
(pricey) restaurant. Bedwell has a better (pricier) restaurant. I like
anchoring out but I also like eating out! You can do both - each to their
own.

Cheers.