zram
minimal template. don’t install unnecessary services.
get rid of X if the sys-qube doesn’t need X
don’t use usb-qube if you don’t need it.
don’t use sys-whonix when you are not updating a qube.
lighter browser for unimportant browsing… midori’s development stopped at 2019. 
w3m if you only need to read the text.
maybe get rid of swap. my laptop has a small ssd and only 12 gb ram.