Christmas market timing around Stuttgart

Since it does get dark early, the lanterns and torches will be lit around 16:00 in Esslingen. Go a bit early in the day time, walk around, wait for the lanterns, then head to Stuttgart for a few more hours in the evening. You can do both markets after dark, when they are the most beautiful.

Thanks Ms. Jo! I knew you are one who had been to both markets and was hoping to get your advice!

In Stuttgart, they decorate the roofs of the huts in elaborate fashion. When it's dark, it's harder to see the decorations, as they weren't lit when I was there precovid.
Esslingen should have a schedule of events, as it's more like a festival. You'll want to see the parade, the fire juggling, the alchemist, the children's area (skill games and crafts,) and the stage events schedule. We were dancing in the street to a Middle Ages band, had no idea what they were singing, must have been the gluhwein, but it was a fantastic time. One area does not use electricity and all lighting is by fire. Friday and Saturday nights will probably be packed, but there's no avoiding being somewhere on a weekend.
Ludwigsburg was very underwhelming when we were there in 2019. It's also a walk from the train station, so treat yourself to a taxi, if you go. It was under 10 euro then.
There's a lot of being on your feet, and not alot of places to sit, so pace yourself. If you see seating, rest and have some gluhwein. Shop during the day, because the crowds come as the locals get off work.
You'll have a magical time. I can't wait to return. Enjoy and safe Travels!

And Stuttgart is not far from Strasbourg and Colmar, which are also unforgettable. They decorate every floor of the buildings, up to the roofs, and the streets have waves and waves of colored lights across them. I think Strasbourg old town was the most decorated town I've ever seen! I'll attach my 2019 Trip Report, and forgive me if this is repetition.
You've really making me want to return!

https://community.ricksteves.com/travel-forum/trip-reports/christmas-markets-switzerland-france-germany-2019

Thanks Pat! Good to know about Ludwigsburg. We'll probably skip it. Lot's of good info on Stuttgart and Esslingen also - thanks! We will be spending 2 nights in Colmar prior to Heidelberg. We've been before in the summer and my husband was insistent we add it to this trip as we suspect it will be very magical with the Christmas markets! We have a day tour planned to take us to some of the surrounding villages so excited for that also! Our last Christmas market trip was in 2014 so I keep wondering how things will have changed since then.....more crowded?

If you're not sure about spending the whole 2 days in Heidelberg I suggest you seriously consider taking a short train ride from there to Neustadt (Weinstrasse). This is a fairly large "romantic" market, in the wine region, where you'll find stuff you won't see in Stuttgart (like vintner's making up their own gluhwein recipes vs. commercial stuff.) It's only slightly smaller than Heidelberg, and yet very different. I prefer this to Stuttgart. (I do go to Stuttgart, but the Porsche Museum is usually my focus, even in December.)

In Heidelberg, I recommend taking the train to the "Altstadt" stop, and then walking back towards the main station. You can detour up to the castle, which has a great view at night if the weather's clear, but otherwise the layout of the various sections pretty much follows the car free zone paralleling the river.

Bad Wimpfen is pretty small, I can't see spending 2 nights there.

Thanks KGC. I'll keep Neustadt in mind should we find ourselves with extra time in Heidelberg. I was planning on going to the Aldstadt train station as we are staying at the Hollander Hof which is closer to that station.

Thanks for reinforcing my decision about not staying IN Bad Wimpfen. We'll get to see a lot more this way.

OP, please forgive me for piggybacking off your post! @Ms Jo, how much time would you recommend in Esslingen?

I arrive in Stuttgart (staying near the HBF) at 10am so had originally planned to go straight to Esslingen after dropping bags at the hotel but after seeing your recommendation, wondering whether to spend the morning in Stuttgart before heading over to Esslingen.

Current plan for Esslingen was to see a few of the sights like the Inner Bridge, St Dionysus Church, Castle and Ramparts, though I expect that wouldn't take more than 1-2 hours maybe?