As to the singers, they just lost Yui, Moa is still the backup, but Su is the voice of the band for sure, don't think there'd be a Babymetal without her.
The singles still stand out as favorites for me, especially Monochrome, Metal Kingdom, and Divine Attack. Monochrome especially is, for me, a masterpiece track, balancing a very heavy theme (the bombing of Hiroshima) with a tinge of hope. I highly recommend watching the lyric video for that one, it's really well done.