How do VA and W ratings of UPS supplies compare with mAh ratings for power banks?
To make an &quot;apples to apples&quot; comparison, you'd need the capacity rating for both devices in watt hours.
What you have is VA for one device and mAh for the other.
VA (volt amperes) and watts are a power rating.
mAh (milliampere hours) is (sort of) an energy rating.
The unit &quot;watt&quot; doesn't have time factored into it.  Energy always has time factored into it.
You can't compare the two ratings without more information than you've given.
A UPS will often have a power rating and a time rating (600 VA for 10 minutes, for example.)
The powerbank rating is usually the capacity of the battery rather than a rating that directly tells you how much energy you can get out of it for how long.
Energy is the product of voltage, current, and time.
Your power bank gives you the product of current and time for the battery discharge, but doesn't give you the voltage of the battery.
The UPS gives you the product of voltage and current for the output, but no time.
You cannot calculate the available energy from either one, and are missing different bits of information you would need.
You can't really make a valid comparison of the two from the information you are given.  It's like comparing an apple core and an orange skin.  Does not compute.

I'd find a UPS that gives you the VA rating and a runtime.  From that you can estimate how long your devices will run.
Multiply VA by the time in minutes.  Call that E.
Multiply the volts and current for each device to get a VA rating for it.  Add up the VA ratings for all of your devices.  Call  that P.
E divided by P will give you an estimated runtime in minutes that you can expect from the UPS.  It will be somewhat pessimistic because the VA ratings for the devices will be the maximum rather than average values.