The $600 threshold is the point at which Amazon has to send you a 1099-NEC. It applies to Amazon, not to you. It has nothing to do with whether you have to file a tax return or pay tax.
If your net self-employment income is $400 or more you are required to file a tax return, whether or not you get a 1099-NEC. If it's over $432 you will have to pay self-employment tax, even if your income is not high enough to have to pay regular income tax.
When you say that you get SSI, do you mean Supplemental Security Income, or do you mean that you get Social Security Benefits, for either retirement or disability? SSI and Social Security are two different kinds of benefits, but they are both paid by the Social Security Administration. You could get both, but they are treated differently for taxes.
SSI does not have to be reported on your tax return, but being "an SSI recipient" does not necessarily mean that you do not have to file a tax return. If SSI and Social Security are your only income you do not have to file a tax return. But if you have more than certain amounts of other income, such as $400 or more of self-employment income, you do have to file a tax return. If you do file a tax return, you have to report your Social Security income, although only some of it, or possibly none of it, will be taxable. You do not have to report SSI, even if you do file a tax return.
The income from Amazon Vine is self-employment income, not hobby income. You have to report it as self-employment income. It's not clear what you thought would be the benefit of reporting it as hobby income, but you don't really have a choice.
