Glad to hear you're starting cutting soon. I hope to begin my layout table and frame patterns soon as well. Just have one more project for the wife (a mantle) and a few day trips for Wounded Warrior Project(another blacksmithing class!) and the Warrior Sailing Program(a weekend Regatta) and I can finally begin cutting.
I can't really say what is common. I can tell you what I plan to do in considering your questions for my True Grit build.
1. I too will be using 8ft ply. I'm a little unsure what you mean, but when I make the cuts for the hull, I will start from the bow(at least in sizing, if not actually starting there) so that my plywood bends around the bow in as much of a single sheet as possible. I am still up in the air about scarfing vs butt joint, though leaning towards butt joint. No matter the joinery, I want the joint to be in as straight a section as possible to reduce the stress.
2. I am planning on using pocket holes for my deck/sole framing only. Ray Macke has a nice write up on his site for his True Grit on how he did his framing utilizing pocket screws. I liked the way he did it so will be using the same technique for mine. http://dev.egyptian.net/raymacke/TG/CabSole.html
For my frames themselves, i'm following the fastening schedule given in the plans.
3. I will be epoxying the crap out of the gaps in the frame joints but will also have the gussets called for in the plans. Screws will also be used in accordance with the fastening schedule in the plans.
4. If I decide to scarf joint the ply I will build a jig for my router. I'm sure it could be done by hand but with the constant change in grain direction i'm not sure how easy it would be to get done and prevent tearout(use the sharpest blades you can), granted i'm more comfortable with power tools than hand planes at this point. There are many videos on youtube showing you how to build a scarfing jig. Just search "Plywood Scarfing Jig" and i'm sure something will pop up. If you ever created a router sled to flatten big boards/tabletops the concept is the same.
I look forward to following along!