Do you think it could be mealy bugs? Trying looking it up and see it it fits. Some can go after roots. Also I use neem oil it kills mealies and some molds. Hope this helps ( I also use it from a prevenative) someone else will post too I'm sure who might know for sure what it is. :)

Most fungi that grow in or on soil are completely harmless.
Your specimen could even be a slime mould, which is in a whole different kingdom of life (and not harmful, by the way).

If you are worried about it, or aren't sure how to identify it, then neem oil may help get rid of it.
You can mix up an 0.5% solution of neem oil and water and then water the plant with it.
Even if it doesn't get rid of the fungus or whatever that is, neem seems to really encourage plants when watered into the soil. It's like a pick-me-up for them!

I can't speak in regards to the cotton-like substance, but in regards to the fungus, not all fungi are bad. In fact, many plants will form a symbiotic relationship with them via their roots, benefiting both in the process.

I was outside watering my plants and noticed a couple interesting looking yellow mushrooms had sprouted out from one of my larger pots. I just snapped a couple photos and then just let them be.

Your plant looks like it's doing okay. Tho, judging from your photos, the soil itself looks like it's being kept too dry. Under watering can be just as harmful as over watering.