You don’t have to use a spline to “stick” stuff to.
You can derive locations as waypoints to use for a nav invoker with the functions it provides.
Splines are 100% the best way to make pathways for stuff to follow.
Roads, walkways, rivers.
Almost all of them are made with a spline regardless. So having the ability to take that same spline and say “follow this” isn’t something to balk at.
The “proper” way to do it for an NPC would be by creating an AI blackboard that reads a point and adjust the move to command accordingly.
The proper way to do it for a PC - and as an example you can maybe take red dead redemption horse riding with the follow camera function - is to add movement input along the spline.
The proper way to do it with floating objects is to just use a flow map system - mind you, the construction is usually still spline bound, but the object doesn’t care about the spline in this one case.
The subject overall can be a book in itself, but if you look up AI blackboard and NavInvoker you should be able to get started.