Is the 4 TB SSD worth it over a smaller drive?

If you keep large photo, video or game libraries, yes. Most 17-inch laptops stop at 1 TB, so the extra room saves you carrying an external drive. If you mostly stream and work in the cloud, a smaller drive would do.

Is a 17.3-inch laptop too big to carry around?

For daily commuting, yes. It is a desktop replacement best left on a desk, with a smaller machine for travel. The large screen is the point, not portability.

Does the touchscreen work with a stylus?

The panel supports touch input, but stylus support depends on the specific pen and screen technology. Check the pen you plan to use before relying on handwriting or drawing.

Can the RAM be upgraded later?

On many thin HP models the memory is soldered, so 16 GB is what you get. Confirm the configuration before buying if you expect to add RAM later.

How does it compare with a 16-inch MacBook Pro?

The OmniBook gives you a bigger touchscreen and much more built-in storage for the same kind of work. The MacBook Pro is smaller, lighter and generally stronger on battery life and screen quality.

What comes in the box?

Expect the laptop and its power adapter. A stylus, sleeve or external mouse is not normally included, so budget for those separately if you need them.