I think it's worth teasing out the requirements. If the need is solely for getting off the lake in case of no wind, then you are optimizing for long range and low weight (or weight that you can store forward while sailing).
There's no particular need to go have lots of power or to go fast (other than impatience). Having Kayaks pass you or not shouldn't be an issue, because even under sail Kayaks can pass you when the wind isn't ideal (like up-wind, or in lighter winds).
I'm confused about your comment about having less of a wake with a three-blade prop. That sounds like you were seeing the propwash and not your wake. Was your motor mounted too close to the water surface?
With my smaller motor, the only wake I see is from the boat, and that would increase if I were to go faster. The wake I see is totally the same as if I was sailing the same speed. (I have the two bladed "weedless" prop). The problem with stock trolling motors is that they are designed for trolling, not cruising. So I'm not that surprised that a propeller upgrade improve the situation.
I happen to think that a slower motor has the advantage of encouraging you to sail, rather than motor, whenever possible. Where I sail, it's not uncommon for the wind to die down in wide bands. I've learned that it usually comes back in less than half an hour, so instead of frantically motoring into the next wind band, I just take a nap.
Now, if you have currents (rivers or tidal areas, or long lakes where the surface water returns to the other shore when a strong wind stops suddenly) then you might need more speed, or you will never reach any upstream destination. Also, if your requirement included motoring against the wind, you'd need more power. But these were not included in the way bdpvt defined the problem - he asked explicitly about how to get off a lake when the wind dies..