Straight cut and dog engagement are totally separate things. One is tooth direction / profile, one is engagement style.
No syncros in a dog-box tranny. Double clutching and rev matching will become your life. Maybe you already knew that. "Dog-box" engagement is retarded for daily use, and anything outside of purpose built race / track car. Always stick to syncromesh if you plan on driving even almost daily, and want to be able to sell the car at some point.
Straight cut is stupid loud, and has it's own inherent set of problems based on tooth profile and design. Boxersix, myself and RedRoof discussed this at length in another thread somewhere. I'll spare you the repetition.
I ran straight cut 1st-5th, double syncromesh w/ needle roller conversion, on my Mazda. It was loud, everyday, all day. I grew tired of it after 6 months. Hysam Chalak @ PAR is where I got my gearset, and I had issues, multiple times. They didn't want to replace parts or warranty shit, but I bullied them a bit. It seems that early WRX owners had similar issues with PAR / Chalak, so I won't imply that PPG have issues like mine did.