I would say it depends. Mostly they enable the modal editing thing and most commands are available. However, what usually happens is that this integration is only skin-deep and there may be conflicts with the IDE's shortcuts.
In intellij, shortcuts (commands using a modifier) can either be handled by the Vim plugin or by the IDE. You can't choose depending on the mode of vim. I mainly use Vim for the movements, so I don't feel very limited by the lack of "advanced features". However, what irks me is the way words are handled. For exemple, the IDE will be able to handle camelCase and go from one "word" to the next with ^->. Vim doesn't know that.
Another limiting factor is that many people use a bunch of vim plugins. As the vim-mode in IDEs isn't actually vim, those plugins can't be used.
I've never tried, but what looks interesting on paper is the neovim integration of VSCode. From what I understand it actually uses nvim, so that should be able to provide the full vim experience, including plugins.