Hello,
The one time I picked up an online order was during the pandemic so I was offered pickup times in 15 minute intervals. The store had beed modified to only have a wall with windows to come and pickup orders or drop off devices for service. I am not sure if the schedule was a pandemic thing or standard.
Shipping & Pickup - Shopping Help - Apple
"Once you're ready to purchase, select Pick up at Checkout. If you would like to change the pickup location, select Change location, then Continue. Items marked Available Today will usually be ready for pickup within an hour. We’ll send you a pickup notification email when your order is ready to be picked up. In some instances, you may also be able to select a window of time to pick up your order at an Apple Store. This Check-In Window will ensure that your order is available shortly after you arrive. Just check in with a Specialist when you get to the store. If you’re unable to come in during this time window, you can pick up your order afterward, but wait times may vary.
You'll receive a notification email when your item is available to pick up. Please wait for this email before coming to the store."
I hope this helps.