Yes, Flare+ is bigger than Flare, but there are a number of other differences, as well:
Soundcore Flare+ offers 20 hours of playtime vs 12 with the Flare. In addition, Flare+ packs in NFC, a built-in subwoofer, as well as a USB port for charging other devices.
This remains to be seen, but my guess is no.
Yep, the Flare has two 6W drivers and it looks like the Flare+ will have a 25W driver.
Still 4.2, I'm afraid.... And still Micro USB