Starting price represents where the initial exchange rate will be. Price range represents where you are initially depositing liquidity. If your starting price is 500 UNKNOWN / ETH, and your liquidity is between 250 yourToken / ETH and 750 yourToken / ETH, you will be depositing roughly (not exactly due to the ranges actually being exponential) half of your liquidity in ETH and half in your token. In this example, if the price goes to 750 yourToken / ETH, your liquidity position will consist solely of yourToken--all the ETH will be gone from it. On the other hand if it goes to 250 yourToken / ETH, your position will be entirely ETH.
The best starting price will be whatever the best price is. If you are reasonably confident in a semi-stable price, set the starting price there. Any other price will be arbitraged out and your position will lose ETH or yourToken to the traders. You may want to set your initial liquidity from, say, just above the startingPrice to far below it, so that you are providing a lot of yourToken and not very much ETH--but if you do so you will not be providing any liquidity if the price of yourToken goes down much relative to ETH.
In general it's just a kind of hard question, you should first look at what it means to provide liquidity on Uniswap, what the price ranges mean, etc., and then look at how other token launches have done it.
