Strategic voting is all about the size of the party and your calculations for whether or not your core party, the one you really support, is going to win or not. You do that under every system. There's a marvellous book by Gary Cox about strategic voting.
It's slightly more common under first past the post because any party that's in third and fourth place is going to get nowhere in terms of getting seats, but you can also have strategic voting if you're a small party in a multi-member district or in a very large district as well. It's all the calculation.