Is embeddings enough to preserve privacy? If I run the encoder/decoder on device and only communicate with server in embeddings?

No, the original text can largely be recovered from embeddings[0] if you know which embedding model was used.

[0] https://arxiv.org/abs/2310.06816

For a short time maybe, but that kind of activity might look like something interesting enough for someone to target you and remove all privacy from your entire existence.