Narayana achieves the Param padam in yajurveda-
ōm sahasraśīrṣaṁ devaṁ viśvākśaṁ viśvaśambhuvaṁ, viśvaṁ nārāyaṇaṁ
devamakśaraṁ paramaṁ padam.
This universe is the Eternal Being (Narayana), the imperishable, the
supreme, the goal, multi-headed and multi-eyed (i.e., omnipresent and
omniscient), the resplendent, the source of delight for the whole
Param padam, the highest abode of supreme being is used in every hymn related to Lord Vishnu or his avatars.
Sometimes different names are used in Vedas for same supreme being- Apam Napat maybe another way to glorify Lord Vishnu.
Similar to how brahmanaspati of Vedas is similar to ganesha in characteristics, and has differing name than brihaspati.
Some info from wiki-
example in Rigveda book 2 hymn 35 verse 2, described as the supreme
creator deity who originates in the cosmic waters. Apam
Napat has a golden splendour and is said to be kindled by the cosmic
Cosmic water, golden hue over dark body, paramam padam. The hymn is most likely referring to Lord Vishnu, the same characteristics are mentioned in narayana suktam.
Apam also means water, Apam the cosmic ocean or water.