Most all "weed" killers, plant poisons, must be applied to foliage to work, according to the manufacturers. Boring holes in stumps and filling them with a high Nitrogen material has been used by some to hasten the decay of those stumps.
Now is the time to take a good, in depth, look at the soil to see what it needs to become a good healthy soil that will grow strong and healthy plants. Aside from soil pH and major nutrient levels and balance you should know about how much sunlight the area gets, how much moisture the area gets (is irrigation available or must the plants rely on rainfall), what might be planted there? If something that needs a soil pH in the 4.0 to 5.0 range do not amend that soil for plants that need a soil of 6.2 to 6.8.
Organic matter is almost always a help, especially if the soil is compacted and hard to work.
Where in the United States are you? That information will be of much help in what other information is given here. What someone in Minnesota may be told might be different then what someone in Florida might be told.

A fair number of shrubs will come back from the most brutal cutting back, especially if they are old. Why don't you just wait and see if they come back and keep them in better shape if they do? You can, and probably should, put down the compost and wood chips, which will, over time, get the soil loosened up.

Planting in fall is fine - the timing depends on where you are, are kimmsr said. You will need to figure out/find out your freeze dates, and then work backwards. Here in NJ, I would plant perennials and woody plants through late October. Bulbs go in any time from now until November.

Good luck with all of it!

Second the advice not to use herbicide here, unless they resprout AND you don't want them back. If you're trying to replant with other plants, herbicide is the last thing you want there.

I have drilled and put granular fertilizer into a stump and it does work, especially if there's enough moisture. In the desert it will all just sit there and look at ya. :-]

What kind of shrubs? Some will come back from a chainsaw haircut and be all fluffy and pretty.

The herbicide will do nothing for decaying ... covering with mulch and keeping it moist will do the most.

If you can plant around the roots, do it. They will eventually vanish.

"Most all "weed" killers, plant poisons, must be applied to foliage to work, according to the manufacturers."

Not exactly. The thing to have done was paint the fresh cut stumps with Roundup. This is an incredibly easy and efficient way to kill unwanted shrubs--especially invasive exotics such as bush honeysuckle. Unfortunately there is a pretty short window of time to cut then paint. It has to be done before the plant has any opportunity to close off and begin healing the vascular structure.

So, it is probably possible to kill them by drilling into/exposing living tissue and applying Roundup (glyphosate.) You might also be able to cut another few inches off the stumps and get to living tissue as well.

As far as preparing the soil for next year I would put down several inches of compost. Wood chips by them selves don't have enough nitrogen to break down enough over the winter to be helpful.

The manufacturers of many "weed" killers will tell you that the product must be applied to the foliage to be effective.
I have many times seen, from some people, to paint the stubs of shrubs with glyphosate and have seen just as much from the manufacturers that it will not work.
Read, and follow, the directions on the product label. Some products have a surfactant (soap) already added and some do not, but some do not. Those that do not will tell you what to use and just plain soap is usually not the surfactant recommended and could make the product less effective.
Your water may also affect the effectiveness of this plant poison since the hardness of the water may render the active ingredient impotent.

Here is a link that might be useful: Using plant poisons