Several tools stand out for their integration with Overleaf and use of LLMs:
Writefull is directly integrated into Overleaf, offering AI-based suggestions for proofreading, copyediting, and paraphrasing.
Underleaf and LeafLLM are Chrome extensions that add LLM capabilities to Overleaf, allowing you to improve and complete text.
TextCortex AI also uses a Chrome extension to provide AI-driven editing and rewriting within Overleaf.