I wear a size 13. My Rome is 26.4cm wide now. The 156 Legacy is 26.1cm wide, not sure if .3 cm would make a difference, but it might.
size 13...yeah, the Legacy is probably the better choice, an Sl is almost a centimeter narrower.
I dunno about dropping all the way down to a 156 though. That's gonna feel like a tiny little thing and I think you'd miss the 5cm of effective edge when you want to venture outside the park.
To each his own, but I think you're going to notice a big increase in "playfulness" just going from regular camber to RC tech in the same length. Drop a size in length and add in the tech change and the playfulness factor will go thru the roof.
At lower speeds (less force), the cambered tips aren't really engaged on the snow. You're riding on the edge between your feet, making it really easy to turn and spin. Feels like a much shorter board. Great for moguls/trees where the speed is not a concern. Add force/speed and the cambered tips get in contact and boom, you've got the whole effective edge engaged and it rides very close to the same length cambered board. Great for a higher speeds on groomers where edge hold at speed is a concern.
Problem is that shorter boards are a little softer and you're 190. There's a point at which speed is less of a factor and your weight alone will generate enough force to bend the board and engage the tips. Then you're effectively just riding a short cambered board and not really getting the benefits of RC Tech. If you're hucking it in the park all day and just want less board to thrw around, then okay.
I don't know where that magic point is, but I think you'd be fine on the 159. I'm your weight and on a 161. I could see dropping to a 159, maybe...if I had to, but a 156? I'd really notice that on the groomers.