Is the 144-tooth ratchet good for tight spaces?

Yes. The dual-pawl 144-tooth mechanism needs only a small swing arc, which helps under dashes and in engine bays. That is the main reason to pick it over a coarser ratchet.

How does it compare with a GearWrench or Milwaukee mechanics set?

It competes on breadth and ratchet tooth count rather than on specialty tools. DeWalt's set leans on a fine-tooth ratchet and a large piece count; check whether the rival kit includes the drive sizes and deep sockets you actually use.

Is it too heavy to carry to jobs?

At roughly 35 lb it is a bench or shop kit. If you need a road kit, a smaller set or a tool bag with selected sockets makes more sense.

Does it include a torque wrench?

No. The torque figure in the specs refers to grip on rounded fasteners, not a measured torque setting. You will need a separate torque wrench for spec'd fastening.

What drive sizes does it cover?

The set is built around 3-drive mechanics tools with ratchets and sockets across the common sizes. Confirm the exact socket list if you need specific deep or metric sizes.

Is it rated for professional use?

DeWalt markets it as professional-grade and aimed at mechanics and harsh environments. Note that the spec sheet says it is not certified to ANSI or OSHA standards.