Lived and living in Cromer for 46 of my 59 years. Biased I know, but love the place and wouldn’t live anywhere else.
There’s a ridge called Cremer’s drift that runs along the coast which is a bit of a ball ache if you’re cycling from the coast inland, but very manageable and not exactly of Peak District proportions!
If you’re looking for somewhere a little quieter and less touristy, I’d recommend Northrepps, Southrepps, Aldborough or West Beckham, or somewhere like Overstand which is a coastal village a mile and a half East of Cromer. Of the larger towns Sheringham is very nice or Wells next to sea further West.
I’m the Secretary of North Norfolk Wheelers. We have four organised rides a week if that’s your thing. North Norfolk has miles and miles of criss crossing country lanes mostly traffic free. Not exactly ideal if you’re worried about average speed and flinty mud on the roads during winter can provoke the puncture fairy, but I love it!