You can always see a nice graphic showing the broad breakdown of Fed asset holdings at the Cleveland Fed’s website:
Source: Cleveland Fed, accessed 2/1/2022.
A short time series on remittances to the Treasury of earnings on Treasury assets is reported here (h/t pgl):
Source: US Federal Reserve.
For clarity, “taper” means reducing the pace at which new assets are purchased. That means the new purchases will end March 2022.
In the last reduction in the Fed’s balance sheet, as shown in the first figure above, holdings of MBS’s were reduced by allowing the securities to mature, without replacement.