Wish + Glyph of Warding

[ATHATH]

Spell Glyph. You can store a prepared spell of 3rd level or lower in the glyph by casting it as part of creating the glyph. The spell must target a single creature or an area. The spell being stored has no immediate effect when cast in this way. When the glyph is triggered, the stored spell is cast. If the spell has a target, it targets the creature that triggered the glyph. If the spell affects an area, the area is centered on that creature. If the spell summons hostile creatures or creates harmful objects or traps, they appear as close as possible to the intruder and attack it. If the spell requires concentration, it lasts until the end of its full duration.

The basic use of this spell is to duplicate any other spell of 8th level or lower. You don’t need to meet any requirements in that spell, including costly components. The spell simply takes effect.

Can you load a Glyph of Warding with a spell whose effect you're using Wish to duplicate, or do you need to actually have that spell on your spell list to load it into a Glyph?

Also, if a Glyph of Warding casts, say, Planar Binding, is the affected creature bound to the will of the caster of the glyph or to the "will" of the glyph itself?

[No brains]

Can you load a Glyph of Warding with a spell whose effect you're using Wish to duplicate, or do you need to actually have that spell on your spell list to load it into a Glyph?

Not quite because you would need to cast 2 9th-level spells. You need to cast Glyph of Warding at the same or higher level than the spell that it is storing and I think Wish is a 9th-level spell even if it replicates a lower-level spell. If you have a scroll of Wish, or some other way to have an extra 9th-level slot, you could probably store Glyph of Warding; Wish; [some other spell.]


Also, if a Glyph of Warding casts, say, Planar Binding, is the affected creature bound to the will of the caster of the glyph or to the "will" of the glyph itself?

Ask your DM. Some would want to obstruct this combo to preserve the flow of the game and may resort to this as an excuse. It's sensible to want to keep D&D from turning into 'tenuous pokemon with fiends', so if your DM doesn't let this fly, don't get on their case.

That said, I believe it's still you 'casting' the spell and so the creature would be bound to you. There seems to be two usages of the word 'cast' in the text of GoW. The first usage is the expenditure of resources to begin and maintain the spell effect while the other usage is 'the release of of a spell at the end of its casting time'.

Most of the time, you cast a spell and the spell is cast before the action is over so there doesn't need to be a difference, but with longer casting times and GoW, there seems to be a distinction. I'll highlight examples below.

Spell Glyph: You can store a prepared spell of 3rd Level or lower in the glyph by casting [usage 1] it as part of creating the glyph. The spell must target a single creature or an area. The spell being stored has no immediate Effect when cast in this way. When the glyph is triggered, the stored spell is cast [usage 2]. If the spell has a target, it Targets the creature that triggered the glyph. If the spell affects an area, the area is centered on that creature. If the spell summons Hostile creatures or creates harmful Objects or traps, they appear as close as possible to the intruder and Attack it. If the spell requires Concentration, it lasts until the end of its full Duration.

If there isn't a dual definition of 'cast/ casting' then a stored Conjure Elemental would go off one minute after the glyph is activated, as it has a casting time of 1 minute. Of course, this is also a sensible interpretation, as well as one that can restrict players from trying to bind fiends without assistance. A Glyph of Warding with Planar Binding that subscribes to this interpretation would successfully bind a creature after it stayed within range of the Glyph for the entire casting time.

[ATHATH]

Not quite because you would need to cast 2 9th-level spells. You need to cast Glyph of Warding at the same or higher level than the spell that it is storing and I think Wish is a 9th-level spell even if it replicates a lower-level spell. If you have a scroll of Wish, or some other way to have an extra 9th-level slot, you could probably store Glyph of Warding; Wish; [some other spell.]
Note that, according to Sage Advice, Twinning a spell that Wish is replicating requires a number of SP equal to the level of the replicated spell, not Wish (https://www.sageadvice.eu/2016/04/04/can-you-twin-a-spell-duplicated-with-wish/).

[HPisBS]

If you use a standard Wish, you say "I Wish to cast [Planar Binding] as an 8th level spell."

You then instantly cast an 8th lvl Planar Binding. So Planar Binding is then 8th lvl. Not 5th lvl, not 9th lvl. 8th lvl, because that's how you cast it. (Which is extra appropriate, because if it were 9th lvl, it'd last a year and a day, rather than just 180 days.)