For screws, an impact driver will work just fine.
For bolts, as Ecnerwal points out, you need to drill pilots, so there's really no need for an impact wrench for that, either.
xster makes a good point that we should probably agree on terms first. The "traditional" lag bolt is, technically, not not a bolt at all, but a screw. Usually 1/2 dia for attaching ledgers and require washers be used with them:
You typically need to pre-drill for these to avoid splitting and just making them able to be screwed in. With proper pre-drilling, an impact driver should work fine, but there are arguments for going with an impact wrench.
Today, however, there are a lot of products that are designed to take the place of a traditional lag screw for things like attaching ledger boards:
These have an integrated washer and a narrower shaft and are designed to be drilled straight in without a pilot hole. For these, I've found an impact driver works just fine, and would actually worry that an impact wrench may actually have too much torque for the narrower shaft. In the case of this particular example product, Ledger Lock, the manufacturer points out that a cordless impact driver is all you need.