Do they look anything like this?
This is a video of the mulch in my no tills.
These are hypoaspis miles, predator mites, they eat any pests like spidermite eggs, fungus gnat and thrip larva. they're definitely beneficial. If the white ones are as fast, but smaller, they're probably just immature, if they're slow moving and look like eggs, they're the type that feed on decaying organic matter and are also nothing to worry about.
An important thing to note is that if the bugs are feeding on decaying organic matter, or feeding on the bugs feeding on that matter, it's highly unlikely that they will attack living plants. Bugs that like living plants, don't like dirt, they like sweet sap and vice versa.
I know you can get pests from bagged soils and compost, but I think these invade during poor storage conditions. I doubt they'd invade a homemade soil mix while it's cooking.
