I got it. For those who will seek it later
(1) qubesctl saltutil.sync_all (initial setup of salt)
(1.5) qubesctl state.sls qvm.default-dispvm qvm.default-mgmt-dvm (installing default dispvm and mgmt vm for salt)
(2) qubesctl top.enable qvm.sys-net qvm.sys-usb (configure your system to have sys-usb and sys-net)
(3) qubesctl top.enable qvm.sys-net-as-usbvm pillar=True (configure that sys-net and sys-usb is one vm using configs in pillar directory)
(4) qubesctl top.enable qvm.disposable-sys-usb qvm.disposable-sys-net pillar=True (configuring sys-usb and sys-net to be disposable)
(4.5) qubesctl top.enable qvm.usb-keyboard (enabling usb keyboard to work)
(4.6) qubesctl top.enable qvm.sys-usb-allow-mouse pillar=True (enabling usb mouse to work)
(5) qubesctl state.highstate (executing configured setup)
Done. You have sys-net and sys-usb in one vm and disposable via salt.