

As other commenters have said, its about as strenuous as doing two normal installs.
However, if you want to do this challenge but feel guilty about the consumed resources, consider donating to the two distros you are performing this with to cover any additional service costs. In all likelihood it’ll only cost them fractions of pennies, but any reason to donate to FOSS is always appreciated.
The beauty of this exercise is you can make it as easy or challenging as you want just by changing the targets, and finding different combinations can keep things interesting.