As noted in many other reviews, this laptop bag is not a carry-all one-size-fits-all. I find it works fantastically has a laptop sleeve++. It holds everything I need to work from a coffee shop, or a quick trip into the office. However, it is not a replacement for a backpack or full-sized shoulder bag.
The stiff backing materials used on the outside of the clamshell, and the width of the material around the zipper will prevent you from zipping anything bulky into the case. This has improved over time for me as the materials has loosed with use, but you may have to choose *which* accessories you take with you.
I have the Small bag and back the following:
Macbook Pro 14 Inch
Spiral Notebook
Pen
Macbook charger brick and cable (fit depends on *your* charger)
Battery bank, and variety of USB Cables
External SSD drive.
Collapsable mouse.
I can fit a full height mouse if I'm careful with the zipper, or comfortably if I remove the notebook. I have an external monitor, but it is far too large to fit, a thiner display *might* fit next to the laptop depending on dimensions.
There *is* an special spot for an Airtag like the other LTT bags (the location is left as an exercise for the reader).