Polperro is a lovely stop over and well worth the run out.
I did the same trip a couple of years ago in a 24 footer. Planned trip was Plymouth to Polperro and stay on the visitors buoys the night. We had a lovely run across but on arrival there was only one buoy available and it was the furthest out. Not a major problem but too rolley for a night in a 24' boat. We stayed for an hour and untied and went to Fowey. Lovely run along the coast and not much further to travel. Spent 2 nights at Fowey on a visitors buoy.
You might find the buoys are taken by local vessels at Polperro at low water waiting for the tide to re enter the harbour. So best have your back up plan ready.
Fowey is a great bolt hole with plenty of visitors buoys and a water taxi.
Having done this trip before, for the small extra distance, if weather permits, I would certainly make Fowey plan A
As Lakeland said, if tides are correct, you could shoot down on the last of the ebb and then back on the flood. Sounds like a lovely run our