You can programme using Visual Studio (see the documentation under Gamestudio SDK section), it's possible to control engine scripts and even write entire games in C++ if you know hwat you are doing.
However, the SDK looks cumbersome to program (at least to me it is) and I am waiting for them to implement DLL functionality in LiteC ... it will be much easier to wrap the engine using this way.
As for intellisense/autocomplete I cannot answer that as I don't use Visual Studio.