I think my favourite view of the Estuary is from Sowden End in Lympstone parish where the road dips to the beach. To sit on one of the benches above the wall there and to look out at waters not too fussed by boats, moored or moving, is a great joy.
Thomson and Clark in their 1934 book The Devon Landscape suggest a few places from which to view the Estuary.
"Every tide and passing cloud seems to bring some fresh beauty to this fine estuary, whether viewed from the heights by the Belvedere on the Haldon ridge or from the riverside at Topsham, Lympstone or Starcross. We have already written of the commanding view of the river from Woodbury Common, but another, hardly less satisfying, is that from the Beacon at Exmouth looking westward across the silvery-blue waters of a full tide to the hilly background of Great Haldon."
Which last reminds me of the story, I found it in Burton, The South Devon Coast, that Frederick Temple, when he was Bishop of Exeter, stood on the steps of Exmouth vicarage and observed drily, "Exmouth is a good place to look - from."