I can use XMRig.com or even XMR-Stak to mine with multiple GPU's right? I prefer Arch Linux/Ubuntu but does Hive OS take any fees?
Ubuntu is a good option if you know what you are doing and are experienced with mining.If not then for most beginners Hive OS is the perfect choice as most option are already there for you to choose from the community that have chosen what is the best overclock or undervolt setting without you needing to experiment with it.
As already said for one rig Hive OS is free and even if you have multiple rigs the cost to have them all running Hive OS is irrelevant when comparing the ease of use of such system.
The cost of Hive OS is $3 per month. If a mining farm brings in a dollar per day without taking into account expenses, and electricity costs $18 per month, then $21 in expenses is a lot with $30 in profit.
If there are 2 mining farms, then you can use Raven OS on the second one so that it is free.