Not gonna comment on the middle names, as I don’t think those really matter much (and should ideally be names that honour friends/family or have other strong meaning for the parent/s anyway imo).
But for first names I think that only really Rosalind and Josephine fit the “classic but not in the Top 100” criteria, as they’ve been popular enough in the past to count as classic sounding, they are just a bit out of favour now.
Georgiana, Theodora and Guinevere are fine enough names with lots of history (I especially love romantic sounding Guinevere and it’s spunkier nn Gwen) but are too uncommon to count as classic imo.
“Strong” is more subjective too - but Rosalind probably fits the best as it reminds me of both the Shakespeare character and pioneering scientist Franklin. Josephine might also work as it makes people think of Little Women’s “Jo” March or the Empress.
With 3/4 syllable names maybe think about likely shortening’s to help decide- Roz, Jo, Gwen, Georgie, Thea are probably the most likely (but Josephine, Theodora and Georgiana have the most other options.)
Other similar style names you might like might be Helena, Antonia or Juliet ?