Make clear interaction between this extension and other haskell related ones

I got vscode-haskell to work - for example I can sue Code evaluation, but I cannot see completion. I am wondering what are the additional extensions I should install.
Could somebody add the current list of required extensions to the README? At the moment I have installed and enabled:
- Haskell 1.2.0
- Haskell Syntax Highlighting 3.4.0.
- hoogle-vscode 0.0.7
but not:
Ormolu (0.0.6 or 0.0.10?), brittany 0.0.9
ghcide 0.0.2
hlint 0.5.1
stylish-hindent 1.0.0
Haskutil 0.10.4
Haskell Extension Pack 0.0.1
haskell-interactive 0.6.0.
Haskell Runner 0.4.3
haskell-ghcid 0.3.1
haskell-linter 0.0.6
simple GHC (Haskell) integration 0.1.23
Which of this list of extensions is required for Haskell 1.2.0 functionality (i.e. which one is the one which does produce the code completion?)
which extensions MUST NOT be installed and would interfere with Haskell 1.2.0?
At least the list of what should be installed would be helpful for beginners!
Thank you for the IDE.