Aristois have a CPUminer???
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No, Aristois is not a miner. Since it is loading more stuff than the vanilla game, you can expect usage to be slightly higher.
On my machine (i7-8700k), vanilla sits around 2.6%, Fabric at 2.8% and Aristois around 3%. The only time I see spikes is loading new stuff (which of course happens on Vanilla and Fabric too).
It's also important to note that the usage will be higher while resources are still loading. My main menu sits at around 80% usage until everything is done loading.
Have you compared the results with vanilla and Fabric? In a server? You might want to try allocating more RAM if it's running on the higher end.