Will the new rules affect those already on 5 year route?

Editing this - as looked in the white paper proper
https://assets.publishing.service.gov.uk/media/6821aec3f16c0654b19060ac/restoring-control-over-the-immigration-system-white-paper.pdf

It says: We will continue to offer a shorter pathway to settlement for non-UK

dependants of British citizens to five years, provided they have remained
compliant with their requirements, and we will retain existing safeguards to
protect the vulnerable, including settlement rights for victims of domestic
violence and abuse.

You can read more about it on the other forums, such as on this very large forum-
https://www.immigrationboards.com/viewtopic.php?p=2193249#p2193249