I would choose one that resonates with you and then break it down trying to determine what it is about it that appeals to you. Then practice it and see what you would like to incorporate into your own style.
In terms of classes, for decades I have taken any and all classes in whatever style with a variety of teachers as I learn so many tidbits from each one. But classes are expensive and can add up so it’s best to select what seems like it will give you the most benefit. It’s a shame, I can’t find any advanced Spencerian classes for this year either. There is also the possibility of reaching out to one of your mentor’s and seeing if they offer private lessons.
I would also recommending watching Mike Ward (MGWard)’s videos on YouTube. He has practice sessions and they are so informative!
You will find a bunch of fabulous lessons on his website:
MrMGWard.
Ornamental Penmanship seems the next step if you want to branch off into flourished Spencerian.