Configuration issues Raspberry Pi 4

Dunno about the wifi issue (wifi on the RPi4B sucks). The partition issue is simply that the image doesn't partition the remaining space for you. You need do it manually with fdisk or the like. Just know that if you ever expand your root partition, you risk overwriting the manually created partition. I recommend building your own image and setting the CONFIG_TARGET_ROOTFS_PARTSIZE and CONFIG_TARGET_KERNEL_PARTSIZE to values you will never exceed.

On mine for example:

% grep PARTS 5B-diffconfig
CONFIG_TARGET_KERNEL_PARTSIZE=32
CONFIG_TARGET_ROOTFS_PARTSIZE=512