Are Browning Invector and Invector Plus Interchangeable?

Standard Invector, Invector-Plus and Invector-DS choke tube systems are NOT interchangeable.

Is Browning Invector Plus and Winchester Invector plus the same?

Yes they are the same. Invector Plus is Invector Plus. I have 2 Browning shotguns and 2 Winchesters and they take the exact same chokes.

Does a Browning Maxus take Invector or Invector plus chokes?

Both have the same invector plus choke system. The improved cylinder and the factory mod tubes both throw nice even patterns. I used both in my x2 before putting a patternmaster. When my browning came in the first thing I did was put a patternmaster in the gun.