How many currency units in 1xBTC / 1xAltCoin? Since BitCoin (and AltCoins) are divisible by up to 8 decimal places, does that technically mean that 1xBTC (or 1xAltCoin) is equal to 1 billion individual units of currency?
No, at least not for the original Bitcoin and all those altcoins that do not change this aspect. But you are almost correct: Each Bitcoin is divisible into 0.1 billion (which is 100 million or a 1 followed by 8 zeros) actual units, called Satoshi after the pseudonym of Bitcoin's creator. In fact, the protocol only uses these; displaying them as Bitcoin is purely an output formatting convention.