G'day Duncan,

The difference between the Aeros Premium Large and Premium Deluxe pillows are the size.  The Deluxe is a much large, rectangular pillow, so has more of a 'home' style feel to it.  By default, the pack size and weight of the Deluxe bigger.

The pillow lock system patches comes with all Sea to Summit sleeping mats - you can contact Sea to Summit support team if they were missing from your mat!

G'day Alex,

It can, but in my experience, these pillows only take one or two breaths to blow up so wouldn't be worth using the pump sack bag.  This can be quite large as it's all integrated into the storage sack, and you'd probably only end up with about a 1/3 of the air from it to fully fill the pillow.
Hope that helps.

G'day Liza,

No, the cover material isn't removable, however, the pillow can be hand washed with the cover in place.

G'day Connor,

I'm not sure whether either size will make a difference in terms of being a side sleeper. I guess if you move a bit during the night as you roll onto your side, the large will be a better option.