Could you please be more specific? If you buy the vanilla swaption, your market view should be that the 20y swap rate will go up and its volatility will also go up.
What about the mid curve option. What market view should u have in order to enter to this trade.
Well, I am sure you can answer this question yourself, hence my prodding. The logic for the mid-curve option is exactly the same as for the vanilla.
If you buy a payer, you will make money if the underlying rate goes up. You also make money if the vol of the underlying goes up, but let's get there when we get there.