Best way to use Vim with AI for tab completion only (no agentic coding)?

I want to keep using Vim as my primary editor, but add AI in a minimal, controlled way:

Inline/tab completion : ghost text that I accept with Tab, nothing autonomous. No file editing, no PR creation, no "agent" doing things on my behalf.

A way to ask questions: something like a chat buffer or a command where I can ask about code, get explanations, etc. Again, I'm in control; it only acts when I explicitly ask.

I've looked at copilot.vim + CopilotChat.nvim, Supermaven, and minuet-ai.nvim.

Curious what others are actually running day-to-day. A few specific things I'm wondering:

Is Supermaven the fastest option for ghost-text completion right now?

Is there anything that gives Cursor-style Tab (next-edit prediction) without using the Cursor itself?

Running Neovim on Linux.

Not interested in Copilot Workspace, Codex CLI, or anything that touches my filesystem without my confirmation.