Stick with pruning group 3 Clematis "John Huxtable" or "Huldine" are very wonderful white Clematis...Jeanne

I was thinking John Huxtable, as well!

Carol

I wouldn't mix The President (pruning grp2) with the others listed as they are group pruning grp3, unless it's spaced far enough away that the stems won't merge. Pruning will be a nightmare.

The above mentioned clematis are nice choices.
I'll throw a couple of other names in the pot.....
Marie Boisselot can be pruned either as group 2 or 3 and is a nice white. For a little different flower shape, maybe Kaiu with smallish white bells
Florida seiboldii is pretty awesome although it's not listed as being an easy grower, but I planted mine before I read that and fortunately, my plant hadn't read that either so it worked for both of us. LOL

wanda

I personally don't think Jenn would have an issue treating the President as a type III clematis in her zone 9 California garden so mixing it with other type IIIs shouldn't be a big deal.

Another white option would be campaniflora.