If I were you, I'd choose between the SE or the Plus.
I had an iPhone 6s and the size is too big for a not convincing screen size/resolution and the battery life is the worst of all iPhone models.
With the SE you get the beauty of the 5s design, the speed and camera of the 6s and the most important thing, the great smaller size.
Don't you worry about typing on a 4" screen, my hands are big, my fingers thick but still I can type fast and accurately.
On the SE you won't get 3D Touch, but you'll enjoy its amazing battery performance.
So again, my advice, avoid the 6 or 6s, and go for the SE or the 6s Plus