Glad it’s working. These should be the solutions
a) I think it’s possible the /opt/vc folder is missing or the command alias is. You can try running the full path, “/opt/vc/bin/vcgencmd measure_temp” instead and see if it runs. If it doesn’t you can run “sudo rpi-update” and it should be restored on reboot.
b) You will need to run “sudo raspi-config” and run “extend filesystem” to take up the entire space. The RACHEL-Pi images automatically resize the file system on the first boot, but it only happens the first time. If you’ve cloned a smaller card to a larger card that’s already been run once you’ll have to resize manually.
There are a few things that the Pi4B has that should improve the performance but without USB boot the MicroSD bottleneck is still there. It’s definitely faster for me during development and testing, but serving content requires reading off of the storage device.