Invest but don’t stress
You don’t have to worry about taxes from Angel Investing until one of the companies you invested in has a financial event that affects shareholders. This could be a “liquidity event” such as an acquisition or IPO where they return money to investors - or a shutdown. When this happens, you will know.
The K-1 is the tax document associated with startup investing via SPVs. Tax returns and K-1s are only required to be filed with the IRS if there is taxable income or loss to report for a given tax year. Every platform that supports SPV investing will provide you with K-1s when required. If you invest directly (not via SPV), tax documents will be provided by the company via the cap table management software they use.
Startup investments take a long time to bake. It will be a minute before all this becomes important.