You can see if an ACATS transfer is an option. If you are holding publicly traded stocks, bonds, ETFs, and some mutual funds then everything would transfer without incurring taxes. But proprietary mutual funds might not be able to be transferred or might incur significant transaction fees at your new firm. I think I remember Schwab had an ACATS request form that allowed the user to check what would transfer and what would have to be liquidated before the request was actually submitted. Fidelity might have a similar tool, but otherwise that information should be similar between any pair of institutions. https://www.investopedia.com/terms/a/acat.asp

Yes, TreasuryDirect is for I bonds, that interest rate has been too good to ignore. But don't consider it an essential account everyone must have.