Yes you could do that but I tend to look at it as Plumbing Fixtures are the terminal equipment, Plumbing Equipment (which was only recently added to the available categories) is main equipment such as water heaters, storage tanks etc.
But do whatever works for your requirements.
For @c_liuKKMVV 's benefit, in terms of your initial query, different categories are treated as "underlay" items in different view classifications which is what was causing your initial visibility problems. Changing the family to a MEP classification removed the underlay setting when in a MEP discipline view.
See this link for more information:
https://help.autodesk.com/view/RVT/2026/ENU/?guid=GUID-5D8831F6-6F15-4BF3-ACEB-06FBC14A5491
Excerpt:
