I am considering filing an inheritance declaration and paying the associated inheritance taxes. Does this filing imply tacit acceptance of the inheritance ?

In principle, no. If filing an inheritance declaration and paying the taxes are not listed in Article 784 of the Civil Code (which lists acts that do not imply tacit acceptance), old case law has considered that these actions do not constitute tacit acceptance, provided that the taxes are paid with personal funds (mainly in this sense Cass. civ. July 7, 1846)