What happens to bitcoin when Segwit2MB activates? Specifically what will happen with bitcoin in wallets. Do I have to try and quickly buy "Segwit coins" if the value of bitcoin core drops?
Do I have equal amounts of Segwit and core coins?
If so wouldn't that initially double how much I have assuming the value is the same initially? 
Is it even a hard fork? 

If the answer isn't relevant to Segwit2MB than what happened with Ethereum and Ethereum classic did it hard fork and I have the same questions about it.

Sorry if my terminology is poor
In the event of a chain fork, any Bitcoin that you have now before-the-fork will also exist after the fork on both chains. So if you have 1 BTC now before-the-fork and segwit2x activates causing a chain fork so there is segwit2x chain and non-segwit2x chain, then you will have 1 BTC on the segwit2x chain and 1 BTC on the non-segwit2x chain. However spending your 1 BTC on either chain can result in the 1 BTC on the other chain being spent too since the transaction would be valid on both chains because you are spending a coin from before-the-fork. This is known as transaction replay.