Welcome to the forum! You've actually asked a lot of separate questions. And there are several good answers to them all.
If it is now time to move to taxable account investing you can
-rework your 401k to better choices (it is possible but unlikely that Fidelty 2040 is your best choice) so that you don't need to hold bonds in your taxable account at all
-use Total Stock, Total International Stock, and I Bonds in taxable (but I bonds have a limit each year)
-use Total Stock, Total International Stock, and tax-exempt bonds in your taxable account
Option 1 has been the most common "best" answer as long as I've been around. Option 2 has always been considered a good choice, but it seemed that people just didn't want to bother with I Bonds in the past (although that seems to have gone away in the last year or so). That leaves Option 3 which used to be the "wrong answer", but now seems to be more acceptable since some tax-exempt bonds are paying better these days than taxable bonds.
I would suggest you take a look at what else is available in your 401k. As I said above, it is unlikely the target retirement fund is your best choice. People here could help you set up your 3 accounts as one portfolio.
I would just buy Vanguard mutual funds at Vanguard. Easy to do and no transaction fees. There are places you can get Vanguard ETFs with no transaction fees, but I don't think e-trade is one of them.
Invest in what you want and don't worry about the difference between Investor Shares and Admiral Shares. The cost difference is not great and you will work into Admiral Shares in a year or so.