A:AnswerYes, but you may need a BIOS update.
To check CPU support and its BIOS requirements, please refer to:
https://www.asus.com/us/Motherboards/ROG-STRIX-B450-F-GAMING/HelpDesk_CPU/
A:AnswerWhen the M.2_2 is occupied by M.2 device, PCIe x16_1 will run at x8 mode. https://www.asus.com/us/Motherboards/ROG-STRIX-B450-F-GAMING/specifications/