Among the relevant PHB quotes, you should take into account that "hidden" doesn't mean "unnoticed". When you cast a spell, you stay hidden but you reveal your position. So under some circumstances, you can still benefits from being hidden (creatures have disadvantage attacking you) but they know your existence and position. You're trying to replicate the setup (being hidden while casting a spell) that triggers the "magical ambush" ability from the Arcane Trickster subclass, of which Jeremy Crawford explained (I won't say clarified because it was already very clear) that "The intent is that you benefit from being hidden but then reveal your position." So the material component DO matter, because it forces you to reveal your position, while staying hidden. So you can be counterspelled, for example, if someone has a reaction available.
If you cast a spell through Subtle Wish, which doesn't involve material component and whose verbal component is neutralized by subtle casting, you could remain in the shadows and not give away your position (you're just wishing in your head that Bel Shalor should be bound to you as per the standard spell upcast to 8th level).
This doesn't mean that the target can't know where you are, how many of you there are or anything, but does it mean that the subject of the spell notices an effect? It depends on the spell. A fireball has an obvious effect. A Planar Binding has not, but you have to give a perceptible order to the creature for it to have any effect. Planar Binding doesn't convey the order, you're still expected to give the actual order. And doing so, you need to be perceived by the target (who couldn't act upon an imperceptible order because it wouldn't perceive it, you know...) And that's where your plan usually fail: unless you happen to succeed on the first time you cast the spell, you give your position when you do the next step (giving your order).