How to open an app on login on secondary screen?
Assign to Space


Go to the space you want the app to open in (in your case the second space)
Right click your application's dock icon
Move your cursor to "Options" Under "Assign to" select "This Desktop"


Window position and size control

I Googled and found a solution for the resizing issue. (Source)

Make your application launch via an Apple Script!


Make a script similar to this:

tell application "YOUR APPLICATION NAME"
    launch
end tell
tell application "YOUR APPLICATION NAME"
    set the bounds of the front window to {0, 22, 800, 1024}
end tell

Save it as "Application"
Put the saved application in your Launch Items instead of the program itself
Additionally you may undock it with Dock Dodger to make this script run silently.