I live on the IOW. I followed the coastal footpath pretty much the whole route. The only bit I missed out was Seaview to St Helens because its mostly unrideable and really slows you down.
I did it one September and left about 9am, got home about 8pm having run out of light near Wootton.
I did it clockwise, but it depends where you start. I live in Ryde, so got the hilly bits done towards the first third of the ride.
The bit between Chale and Compton is particularly boring, but its over soon enough as long as you arent heading into the wind.
You’ll need to head inland a bit from Shalfleet to the East side of Porchfield as there aren’t any ROWs around there, so probably best to road that bit.
There aren’t many shops nearby in the Ventnor to Freshwater section, so make sure you have plenty of water when you leave Ventnor, Yarmouth to Gurnard is similar.
I think the total mileage for the day was around 73.