I will make an effort here to weigh in, as an active CPA and tax preparer. As @hoopoe said there is no simple answer and…it depends.
You can report the $2000 on schedule C as self employment income. Yes, you get dinged with the self-employment tax but many people get the benefit of the 20% QBI (qualified business income) deduction. IF you fall within the threshold (read again if) then you get 20%, in your case $400) deduction on the front page of your 1040, before tax is calculated. This is our typical practice, even for someone who consulted one time and had reportable income. You do not need to enter additional expenses against the income. But if it isn’t on Schedule C (or a 1120S, 1065) then you don’t get the QBI benefit.
Even income reported on a 1099 can be considered self employment income. It depends on the nature of the income. 1099 INT, 1099 DIV, 1099 B are generally investment income (not subject to SE tax). 1099 MISC are now nearly exclusively used to report rents and royalties (so it depends NII tax or SE tax). The new-ish 1099 NEC (non employee compensation) is generally the catch all for individuals who perform services like consulting, marketing, repairs…horse leases. BUT if the 1099 is issued to a corporation or partnership, it is considered ordinary income, not subject to SE tax. Again…it all depends. 
I will take a stab at this one too. The general stance is that credit card rewards are earned and are considered a “rebate” instead of income. You have to spend money to get the points, airline miles, cash back…but there is a requirement to earn them. Sort of like a rebate for contact lenses or Gastrogaurd. BUT if you get $X for opening an account, that is unearned and should be reported as income. Clear as mud, huh?
Please note that I am speaking in very general terms. This is not tax advice…but one professional’s understanding of the tax issues on this thread.