I remember this is an age old question, and there used to be smaller firewall VM available, not sure now, I just got back to Qubes.
I can’t imagine 1GB of firewall rules, let alone 4GB of rules.
I just lowered the max mem to 1GB. I’ll keep an eye on it. Right now, it’s using 248M. Hard to imagine it needing much more than that.
Not necessary at all. ~600MB is more than enough
I already lowered it to 500MB. If I break something, should be an easy fix.
For most VMs, you can lower it considerably. For example, most sys-* VMs are fine with ~600MB, if you’re just browsing with firefox in a VM 1.5-2GB is fine, etc. Technically, Qubes should manage the memory but in my 6 years of experience it isn’t the smartest at managing memory, especially when you have tons of VMs open.
sys-usb may need substantially more, depending on the kinds of devices and data that are being routed through sys-usb.
If you don’t really use sys-usb, except for occasional usb-pen-drive usage, it can probably be set lower than the default, but just remember you may need to adjust it later if your usage changes.
Just FYI.