Dynamic Re-Ranking (DRR) pins qualifying items rather than boosting them. This pinning is applied after merchandising rules that boost products.
Therefore, if a product is manually boosted by a rule, DRR can still change its position. In other words, DRR will override boosting.
Only rules that pin items will override DRR and therefore DRR will not override manual pinning. This means only manually pinned products will stay fixed and remain unaffected by DRR.
For more info, see our documentation on DRR and relevance.