Anything paid to you in return for a service that you provide is taxable self-employment income. Even though Twitch calls these payments "donations", you are paying a service (providing entertainment) and so the money is considered your taxable income.
All your self-employment income is taxable regardless of whether or not it reported on some kind of 1099-R.
Royalties (payment for re-using past content?) is taxable income just as payments for current content. I believe Turbotax Self Employed version will give you separate places to list current income and royalties but they are both taxable.
Bits are taxable income at their US$ conversion amount as of the day you "constructively receive" the payment. I don't know what you have to go through to cash in a bit. If you can only cash them it at certain times, then the income would be reported on the first day after receipt that you could have converted them to cash, even if you didn't convert them on that day. If bits are immediately convertible to cash, they are counted as income received on the day you received them (at their conversion value) even if you don't convert them right away.
