Well the screws are fuel screws. Turning them out makes the idle mix richer. So when you turned them out, more fuel got in which will decrease rpm. Start off by pulling the carbs off and rebenching them. When you do it, if they are anything like my v45 carbs, use something like construction paper to set the flaps. Set the fuel screws to factory settings and clean the spark plugs.
The screws do not completely cut off fuel to the carbs, so the engine will stay running, it just leans it out quite a bit.
So now, provided that all the passages and everything are nice and clean, you should be able to mount the carbs and start the bike with no issues. From there, a good tach and some tuning should have you going good. Make sure the filter is clean.
As for the noise, it was likely from the bad sync. It makes the bike sound like a washer when idling in neutral. Pull in the clutch and if the noise goes down, that is exactly what it is. So, get some good vacuum gauges and get a close sync and most of the noise should be gone.
The ride IS the adventure. The destination is just to get gas!