WR250R: Yamaha's high-end dual-sport bike, highway-worthy, dirt-capable, road legal in all countries.
WR250X: Supermotard version of WR250R.
This forum is dedicated to the above two bikes.
WR250F: Yamaha's enduro racer, road legal in some countries, not road legal in most US states. This forum does not address this bike.
You therefore need to figure out what kind of riding you intend to do, and then decide on the appropriate bike.
I am also 5'6", and this my advice on lowering a bike: if you decide on the F (or any pure dirt bike), leave it as is. Spend the time to learn balancing the bike and becoming a more competent rider; this will pay huge dividends down the line.
If you plan on venturing in city traffic with an R or X model, then pick a lowering link to bring the seat height to a level that makes you comfortable. Plan on bringing the bike to its original height once your confidence has increased.