Well, a 401k is just a type of account. It just holds investments like the others you mentioned. It isn’t an investment itself. It’s just an empty bucket into which you put stuff.
The Russell 2000 and S&P 500 are both indexes that track the US stock market. An index fund or ETF that tracks those will largely perform very similarly, although the S&P 500 is all BIG companies and the Russell 2000 is all small companies. I prefer the more diversified approach of buying a total stock market index fund (that would encapsulate both of those).
And VT is an ETF that tracks the WORLD stocks. I think it’s a great option, although you’re confusing a lot of terminology and stuff. If I were you, I’d seek to keep it simple and invest in a target date index fund!