I can't claim to have years of experience with fall gardens, but I'm getting a little more each season. Last year I sowed peas in the shade of my tomato rows. Those tomatoes came out a little early and up with the trellis. Cascadia snap peas are nice and quick for fall planting. Early August is the time for that here (6B/7A). This year they may go in first sweet corn block, after picking.
I am also planning to start some cauliflower for fall transplants fairly soon. My brussel sprouts are in the ground (and some pots) for a couple weeks now.
Parsnips are pretty neat, if you have any spot left for root crops get them in ASAP. Black Swallowtails love the tops and lay eggs there. In late fall you can mulch them and dig them up at will throughout the winter.
Here is a chart I really like for general guidelines. This is zone 6, but also look at the zone 7 chart to compare. One example, zone 6 cauliflower is considered spring only, but as I understand for my area, cauliflower is an iffy spring crop that might fail, but a guaranteed fall crop. So, grain of salt, as zones are just guidelines.
https://www.ufseeds.com/learning/pla...nting-Calendar