I have several questions about Imperial ships.
1. How do they communicate, is it like star trek, i.e. com and vid, or is it similar to a radio man relays messages.
We've seen all of those and even holograms is a couple of cases.
2. How do ships 'see' each other, there's images and tactical maps in books/games/pictures, but how do they collect the information.
"Auspex banks" and the like. Where ships are concerned, it seems to be a catch-all term for "sensor arrays" of various sorts. On a normal ship, auspex banks would encompass radar, sonar, long-range cameras, you name it.
3. What is the range of a system defense fleet ships, ...
I imagine the answer to this is the obvious one. They lack warp engines, so they aren't feasible for interstellar travel. That's not to say they couldn't go beyond a solar system... they just couldn't get to another one within the crew's lifetime.
how many ships divided into how many fleets, depending on type of system, i.e. well developed hive system, nonexistent feral world.
Sector-level battlefleets seem to encompass several dozen cruisers, a similar number of escort squadrons (each with 3-6 such vessels), and several capital ships (battleships, etc.). Planets or systems of great importance (such as Armageddon) sometimes command fleets of similar (if not equal) size.
4.How are ships piloted
Bridge crews range from dozens to hundreds of individuals (depending on the ship's size), and include navigators (with a small "n") for real-space travel, pilots to steer the ship, etc. Commands that affect how fast the ship goes and how/when it turns are issued by the captain, who almost always seems to be jacked into the ship via neural connection in the newer novels.