For the most part you really can't do much to protect them while they're in use. You can use thin skins for the exterior but that's about it. Any more than that on the exterior is likely to cause thermal issues since the machine uses the aluminum body as a heat sink.
In fact just about everything you mentioned is known to damage the laptop instead of protect it. I mentioned the issue with the hardshell case and heat but putting anything inside the pid of the machine is more strongly ill advised as it will likely break the display, which is well known for being just about the most delicate in the industry.
I've had one since shortly after release and been fine though. As long you are gentle with the machine you'll be fine. Don't throw the machine around, and make sure you're closing the lid from the center of the display, since it's theorized that added stress on the display from closing it from the side may be the cause of the display cracking issues that a lot of users have experienced.
Below I've left a link to the sleeve that i have, which i use in conjunction to a regular laptop bag. The sleeve i have is not the end all be all. Like if it isnt your style then get a different one, but the sentiment is the same. Keep it in a sleeve, in a bag.
I’ve linked mine below. It works well and protects my laptop sufficiently. Honestly the only complaint I have from it is that it opens vertically lol.
I would like the same thing as you except I carry mine horizontally in a briefcase.
Here is what I got for my M1 MacBook Air.
Keyboard Cover https://www.amazon.com/gp/product/B088H5ZFLN/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Skin https://www.amazon.com/gp/product/B086V7FM3H/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1
Sleeve https://www.amazon.com/gp/product/B08GZZYT2Y/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&psc=1