Is this wrench powerful enough for car lug nuts?

Yes. It is a 1/2-inch drive impact wrench with enough torque for most passenger-car and light-truck lug nuts. For heavily rusted or over-torqued fasteners, use a penetrating oil and the highest speed setting.

Does it work with Makita 18V LXT batteries?

No. It runs only on Makita 40V max XGT batteries. The XGT slide-on mount is different from the 18V LXT mount, so existing LXT packs will not fit.

What comes in the kit?

The kit typically includes the wrench, one or more XGT batteries, a charger and a carrying case. Check the specific kit listing for battery count and capacity, since Makita sells several configurations.

How does it compare with Makita's 18V impact wrenches?

The XGT model offers more torque and larger battery capacity than the 18V LXT wrenches, at the cost of extra weight and a separate battery platform. If you already own LXT tools, an 18V wrench is the more economical path.

Can it be used for light assembly work?

Yes, if you use the lower speed settings and a torque-limiting accessory. On full power it can easily over-tighten small bolts, so match the speed to the fastener.