clangd LanguageClient vs ClangCodeModel: duplicate errors, configuring clangd warnings

Sorry if these are more questions than bugs, but at least better docs would be in order:

1. When I have both ClangCodeModel and LanguageClient plugins on, and clangd language client configured, I get duplicate error annotations (see screenshot). I suppose I have to disable ClangCodeModel plugin when I enable clangd LanguageClient, right?

2. Where do I configure warnings for clangd LanguageClient? Tools / Options / Analyzer / Clang Tools does not help: could not neither turn on "unused parameter" as on screenshot (no warning when ClangCodeModel is off), nor specify -Wno-c++17-extensions (warns about nested namespaces when LanguageClient is on).

Thanks.