I'm assuming you already bought the Flatline barrel. That is bad news, since there are Flatline barrels with Picatinny rails mounted on them. Unfortunately, there aren't many ways to mount a bipod if you can't put a picatinny rail on it somewhere.
No it will not.
Yes, the 98 threaded Flatline Barrel will fit the Alpha black.
Yes. a shroud is just a plastic piece that goes over the barrel.
All you must do is purchase an A5/X7 threaded flatline barrel and screw it in, becasue they have the same barrel threading. 98 threaded barrels will not work.
no
yes
it really depends what your using it for.
It will fit both of them.
They are nearly equal in ability. The Flatline puts a more consistent spin on the ball, but is always on and only does a backspin. The Apex still does a good spin, but can be turned off and adjusted while playing without needing to take the barrel off.
It uses a5/x7 threads but it has a slanted shell and would not fit normally. However an Apex barrel will work just fine.
The Apex barrel is BT's upgrade to the Tippman Flatline barrel. It allows the shooter to "curve" the ball around or "dive bomb" over the top of bunkers by putting a spin on the ball. It also will allow the shooter to get extra distance out of a shot by putting a back spin on the ball. How the it works is the tip of the barrel has a ridge that gives the ball a spin like a curve ball or a spin on a ping pong ball. You can get the same effect by turning a Flatline on the side.
All markers generally go the same distance, unless you have a specific barrel that adds backspin to the ball (apex barrel or flatline barrel). Typically they range in the area of 75 to 100ft. Much of this depends on the velocity.