How Wide the Desk Needs to Be
Measure what is on your current desk at the end of a working day rather than what you use at any one moment. The things that never get put away are what set the width.
A laptop and a notebook need far less than a dual-monitor setup with a keyboard tray's worth of space in front of it. The honest test is whether there is anywhere to put a printed document while you are typing.
The limit is the room. A desk wider than the wall it sits against forces it into the middle of the floor, which is a layout decision rather than a desk decision.
The Top Surface
Most of our desks are offered with a solid wood top, and the Writer's Series adds a leather inlay as an alternative. The inlay is quieter to write on and gives the desk a defined working area inside the frame of the wood.
Wood tops are the more hard-wearing of the two under daily contact with equipment, cables and a mouse.
The limit is that this is an order-time choice. The top is built into the desk rather than fitted afterwards, so it cannot be changed later.
Whether the Back Shows
A desk pushed against a wall only needs three finished sides. A desk facing into a room shows its back to everyone who walks in, and an unfinished back is immediately obvious.
Several of ours are built with a finished backside for exactly this reason, including the Boulder Creek writer's desk.
The limit is that it has to be specified. Decide where the desk will face before you order rather than after it arrives.