I have a ~1 month old set of Steve Harris signature rotosound flats on my fretted Jazz (CIJ ´62 reissue with original MIA fender pickups). The strings are quite thick (E string = .110) and the tension is very high. I was even afraid to tune them up all the way to standard tuning... I bought them originally because I wanted to tune DGCF, but I tuned up to standard tuning anyway after a while. I just had to tighten the trussrod first.
So far I like the sound of these strings, both in D and E tuning. They're still quite bright so even slapping (but not popping) sounds good to my ears; just perfectly lo-fi for my taste.
I have TI's on my Squier vintage modified fretless jazz. They have a much lower tension but they sound good, but more DB-like.
I think as a general rule the lower tension, the thumpier the sound, so I'd go for a set with higher tension if I wanted a less thumpy sound. I just have to add that I don't have much experience in flats so I might be wrong. It's only my engineer mind that want to think it's like this...
I have also once tried a light set of Chromes on a fretless P that I borrowed from a friend of mine a year ago, and they a had quite high tension as well.