It would help if you'd tell where you're located.

True. This all assumes northern hemisphere, and exact dates may vary
depending on how much time you have until cold weather arrives.

Most likely this is a good time to get them in the ground so they can
establish themselves before winter.

Yes, but don't wait too long. As soon as the summer heat is (mostly)
abated, which would be around now or a few weeks from now most places,
is my favorite time for fall planting. Ideally, you'd plant when the
weather forecast calls for several days of clouds and/or rain. If
the plants get hit with heat/sun, just water a lot for the first few
days/weeks and perhaps even try shading with shadecloth or the like
(until the plants stop drooping. The Echinacea will droop quite
visibly, and although it won't really perk up until its roots get
established, it will appreciate the water during this period. Once it
stops dropping, I stop watering it).

Thyme I think is pretty forgiving. At least, I don't think I've
killed one yet. But I don't really remember what times of year I
planted each of them.