This is why I often use an alternate subject line of a product off a marketplace. So many people use the same subject line, so I always know what is going to be inside an email.
As for click-through rate, I've had more success with Solomatic Traffic.
Surfing more than one at a time, Until this past week, I had never tried it myself. 4 is the max I can do at a time. I tried more, like Paula, but it was frustrating.