Hello,
I have owned a Sherpa, Club Tour, Audax 853 and Mk 3 Audax.
The opening question was would an Audax suit my needs better than a Sherpa?
My answer is NO!
A Sherpa is comfortable, can carry the type of loads the questioner carries, it rides with little effort and will go any distance.
The Audax rides more quickly and reasonably comfortably, but in my honest opinion will not do a Camping trip easily.
As an experienced rider particularly of Thorn bicycles, if the questioner wish a great compromise then a Club Tour would be the answer. The Club Tour can be ridden with 28mm tyres or 35mm tyres. It can carry heavy loads. It can be ridden speedily for fun days out or for Audax.
Opening poster, the Sherpa is in my opinion the better bike for you and your needs, that is unless you no longer cycle camp!
Best regards,
John