The old rig T used mostly 1:8 mainsheets, but with the square top mains I believe 1:9 is most common. You need much higher mainsheet tension to make the leech stand up properly with the square tops.

To get top-speed out of a T (or any cat really) you need to be active with the mainsheet, period. On our T I would estimate sheet loads between 20-35kgs at least when we are double trapezeing upwind. Downwind, the spi can be a beast to trim when it is blowing.
If you are not racing, or training for racing, you dont need to be quite as aggressive with your trim.

But like I said in the tilt-trailer thread, also consider what boats you are able to right again without assistance after a capsize. I would not have bought a boat I could not right after a capsize. At 140Kgs, you are a pretty light team, so both the Tornado and the F-18s might be out of scope. I know you would need something extra to right a Tornado with alu mast. About 160 is what I would consider the minimum weight to right a Tornado with alu mast. With a carbon mast, the T is a bit lighter to right, but I dont know how much. BTW: Both the T and the F-18s are sophisticated racing machines. You will need to get pretty technical if you want to race them well. But both will do as recreational boats as long as you follow the basic catsailing rules.