Toras Avigdor for sure. And second favorite is Sichos Yisroel, by his grandson
Personally, I have found that my one chavrusa that is on Whatsapp call is actually quite refreshing. I don’t know what it is, it could be purely the fact that it is simply not zoom and I don’t have to find that link and see that zoom logo again for the 20th time that day. So I like the Whatsapp call all of a sudden. And if you do that, you should make a big deal to the chavrusa that “THIS is your WHATSAPP Chavrusa, and appreciate that!”
You can join the “Jerusalem Kollel” of HaRav Yitzchok Berkovits shlita. We are beginning Hilchos Nidda starting Elul zman. By pesach you will already have semicha in Hilchos Nidda. But you have to join the kollel for both sedarim…