People on the c&v forum here swear by panaracer paselas. I have tried them and they ride great and have good performance, but the sidewall is easy to abrade IMHO. The Gatorskins have the thin sidewall required for high performance but also have an anti-abrasion layer on the sidewall. I abraded the layer going through some gravel in a sidewalk section awaiting concrete, but the sidewall cords underneath were sound. A pasela would have been toast. However, you can just try to remember not to roll through gravel or brush up against sharp pavement.

Some say the latest airless tires are almost as good as conventional tires but others disagree. I haven't tried them.

Go for it, and get a lightweight inner tube also. Plus, provided you avoid sharp edges which can bottom the tire against the rim and thus pinch the tube inside, causing a flat, do not run full rated pressure. Unless you are much heavier than 200lb, try about 65 in front and 75 in back for 27x1-1/4, maybe a bit more if you get 27x1-1/8.

Check if your rims have a hook bead. If not, you can't get a tire which is only for hook bead rims. I don't know if the gatorskin or pasela are for hook bead rims only, since I have hook beads and didn't need to know. It is just a ridge just inside the rim which grips the tire bead.