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).
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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.
