If you are using Elixir <= 1.5 the vscode-elixir plugin will work well. ElixirLS is for >= Elixir 1.6 and utilizes changes within 1.6 for inline reporting of build warnings and errors. I listed my plugins and posted config below. Very basic setup, making use of the keyboard shortcuts, especially vim command mode, save, switch to terminal, switch to code window.

One Dark Pro
Project Manager
Vim
vscode-elixir
vscode-icons

Settings

{
"workbench.colorTheme": "One Dark Pro",
"workbench.iconTheme": "vscode-icons",
"vim.disableAnnoyingNeovimMessage": true,
"editor.fontFamily": "'Input Mono'",
"editor.fontLigatures": true,
"editor.fontSize": 16,
"editor.tabSize": 2,
"editor.renderWhitespace": "all",
"editor.cursorStyle": "block-outline",
"editor.tabCompletion": true,
"editor.rulers": [
    80, 100
],
"editor.autoIndent": true,
"editor.cursorBlinking": "phase",
"editor.minimap.enabled": false,
"vim.hlsearch": true,
"vim.insertModeKeyBindings": [
    {
        "before": ["j","j"],
        "after": ["<Esc>"]
    }
],
"vim.leader": "<space>",
"vim.otherModesKeyBindingsNonRecursive": [
    {
        "before": ["<leader>","w"],
        "after": [],
        "commands": [
            {
                "command": "workbench.action.files.save",
                "args": []
            }
        ]
    },
    {
        "before": ["<leader>","t"],
        "after": [],
        "commands": [
            {
                "command": "workbench.action.terminal.focus",
                "args": []
            }
        ]
    }
],
"vsicons.dontShowNewVersionMessage": true,
"window.zoomLevel": 0
}

I like VSCode with the elixir-ls extension because it gives me fast incremental dialyzer, formatter integration, documentation tooltips on hover and decent Intellisense out of the box without much config tinkering. TBH I’d use vim if I could get it all there that easily.

My VSCode config with some comments:

{
  // Elixir:
  "elixirLS.fetchDeps": false,
  "elixirLS.dialyzerWarnOpts": [
    "error_handling",
    "underspecs",
    "unknown",
    "unmatched_returns",
    // "overspecs",
    // "specdiffs"  // disabled because ecto / phoenix produce too many warnings
  ],

  // Privacy:
  "telemetry.enableTelemetry": false,
  "telemetry.enableCrashReporter": false,
  "workbench.settings.enableNaturalLanguageSearch": false,

  // Editor:
  "editor.minimap.enabled": false,
  "editor.overviewRulerBorder": false,
  "editor.glyphMargin": false,
  "editor.tabSize": 2,
  "editor.folding": false,

  // UI & general behaviour
  "terminal.integrated.fontFamily": "Ubuntu mono", // fixes invisible underscores in terminal on Ubuntu
  "window.menuBarVisibility": "toggle", // show menu only after clicking Alt
  "git.autorefresh": false, // I don't use the integration anyway
  "workbench.editor.enablePreview": false,

  // Search:
  "search.exclude": {
    "**/node_modules": true,
    "**/.elixir_ls": true
  },
  "explorer.autoReveal": false, // Prevents the browser from jumping around when switching files
}

Elixir-LS provides syntax highlighting and has the option to format on save which is awesome.

editor.formatOnSave

Update:

"vim.otherModesKeyBindingsNonRecursive": is now "vim.normalModeKeyBindingsNonRecursive":