Hi :) IMO A Wikidata tag should be the only gateway to access Wikimedia projects on OSM. The ultimate point of Wdata is to provide machine-readable data & links to the same object in different databases, through a stable identifier. 
This basically makes tagging Wikipedia completely redundant. This is only the case for the Wpedia tag though because Wpedia has a much more restrictive inclusion policy than Wdata, so anything that has a Wpedia page should have a Wdata object. it's better to encourage users to update Wdata than to use the Wpedia tag.

in terms of best practice, this is the general trend and view of the Wpedia tag i've seen in the OSM Discord etc. Auto-addition of a Wikipedia tag when adding Wikidata was also recently removed from iD, for the same reasons i've listed 👍