Question on 3LO Authentication

[LewsTherin]

Atlassian now advises all integrations towards a central 3LO OAuth model using a proxy app.
(https://www.atlassian.com/blog/developer/building-secure-and-scalable-integrations-our-guidance-for-third-party-apps).

Currently our customers use PAT for authentication. We plan to migrate to the proxy app by mid-February 2026.

Question:
1. Can we keep using PAT or OAuth using a custom app till mid-Febrauary '26?

2. Given we plan to migrate to 3LO proxy app, would you recommend moving from "PAT" authentication to "OAuth using custom app" in the meanwhile? (before our planned move to 3LO in mid-Feb)