Atmosphere still works with sig-patches if loaded via package3 and hekate. Or you can just use a modded fusee.bin such as this one that I compiled for the latest atmosphere which has ips kip patches support.
No its 2 different file.
Theres 2 method to update the rp2040 firmware, choose one of it:
v2.76.uf2 => This is installed by putting the rp2040 into boot mode (press and hold the boot button and plug the usb to the pc, then release the button)...