I would keep this as a single HR knowledge base unless there is a separate audience, access, ownership, or lifecycle requirement that justifies a second KB.

The publish process is configured at the knowledge-base level, so I would create one custom publish flow for the HR KB and add conditional routing within the flow:

• Articles requiring legal review: Legal approval → KM approval → Publish

• All other articles: KM approval → Publish

I would recommend using a dedicated field such as Requires legal review rather than relying solely on category. Categories are helpful for organizing and finding content, but the legal-review requirement may eventually apply to selected articles across multiple categories.

If the Knowledge Management KCS Capabilities plugin is active, the Governance field may also be worth evaluating. It distinguishes experience-based articles from compliance-based articles, such as policy or legal content that requires tighter control.

Separate KBs would be more appropriate if the articles require genuinely different access controls, contributor groups, owners, or lifecycle rules—not only a different approval path.