You are probably going to be better off emailing or sending a PM to each person individually for AAM right now. The kit is still new and many of the posts on installs for AMM kits have been by shops.
Example:
AAM Twin Turbo Kit Install (2010 Nissan 370Z)
600+rwhp AAM Twin Turbo Build
Z1 Motorsports: AAM TT Kit Installed & Evaluated
One forum member:
Engine (semi) removal on jack stands and AAM twin turbo install.
I would say the kit has been on par with others on the market though hard to know as I have not seen one in person or know anyone personally with the kit.
Many of your questions are not AAM specific but more going boost specific which I can try to help with:
-What is important? Always double the final number, this may not be relevant day 1 but things will break and it will not be cheap.
-The gauges many use: AFR, oil pressure, oil temp, boost (if going E then possibly an E gauge)
-Boost & HP are not always equal, it also has to do with your tune and potentially other bottlenecks in your system (proper exhaust, fuel, etc.)
-Clutch: You will break the OEM clutch, but additional items are flywheel & CSC (you can do Z1 replacement or just upgrade the CSC with aftermarket both have pros/cons)
-Other mods to consider are cooling & exhaust, cooling is oil, radiator (possibly fan upgrade) but also removing hot air from the engine bay with a vented hood or fender liner. Exhaust you will need to pair your exhaust & down pipes with your power requirements.
All the above is also dependent on what you want from boost and plan to do with the car. If you just want a more powerful street car you can skip some items such as a vented hood but if you want to hit the track on the weekends then what I have listed is needed plus understanding additional track requirements possibly needed.