1. The ordering is based on relevance, and the secondary ordering is post dates, newest first. It is not possible to change this, however you can adjust almost every aspect of the relevance, under the Relevance Options submenu.
If however you want to display exact items on a specific post, you can do that too, on the Post editor screen, with the local override options: https://i.imgur.com/7Iq1NYn.png
2. Not by default, but you can choose to get posts with same tags only, on the Relevance Options -> Categories & Taxonomies panel: https://i.imgur.com/x19B2XF.pngBest,
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