Does it fit the Anker SOLIX C300 exactly?

It is made for the C300's footprint, so the station sits snugly. Check the listing's stated dimensions against your unit before buying, since the C300 and C300 DC differ slightly.

Can I use the C300 while it is in the bag?

Yes. The front ports and top handle stay accessible, so you can charge devices without removing the station. Leave the vents clear when the station is running under load.

Is the bag waterproof?

No. The nylon resists splashes and dirt but will soak through in sustained rain. Keep the station under cover in wet weather.

Does it have pockets for cables?

Most versions are a single compartment sized to the station, with little spare room. Plan to carry charging cables separately.

Is it worth it over a generic tote?

If you carry the C300 regularly, the fitted shape and shoulder strap are the draw. A generic tote is cheaper but fits loosely and offers less protection.