How can you retire early if your money is locked up in 401ks that don't allow you to withdraw later in life?

There are ways to get the money out earlier in life. Search for "roth pipeline" or "72(t)".

I am 32 now and want to put 20-50k a year into investments. Can someone point me in a direction of how much this will be in 15 years or how you figure plans?

This is such a broad question that it's hard to answer. 20k-50k is a wide range, and "investments" isn't specific enough to have an idea of what returns to expect.

The basic way to go about this is to pick a specific amount you want to invest (say $20k yearly), estimate what you think your yearly return from your investments might be (say 8%), and what the yearly rate of inflation may be (say 3%). Then you can start doing math like this:

Year #1 = Investment * (1+InvestemntReturn - Inflation) = $20,000 * 1.05 = $21,000

Year #2 = (Year1Total + Year2Contribution)*(1+InvestmentReturn - Inflation) = ($21,000 + $20,000)*(1.05) = $43,050

Year #3 = (Year2Total + Year3Contribution)*(1+InvestmentReturn - Inflation) = ...

... this is a great place to use a spreadsheet rather than doing the math by hand.