If you're in the US, check out EPC's Online Store. They're an electronics recycler and they sell a ton of used electronics.

I've purchased three Lenovo micro PCs (now running my homelab Proxmox cluster) and a micro tower that is a dedicated Plex transcoder.

They have a ton of decent, 3 year old systems that would meet your needs:

1. they're cheap
2. most all come with windows
3. Linux can more than likely be easily dual booted.

They even have some super beefy Xenon laptops.

Edit: this MSI laptop pretty much perfectly fits your reqs.

Second hand professional laptop like ThinkPad.

The framework 16 https://frame.work/products/laptop16-amd-7040

I would advise against a laptop if ergonomics are a factor, they are slightly better than smartphones but still overall bad. Get some basic PC setup (if you don't want to build your own, I suggest an ASUS mini PC or mac mini) and spend the rest on getting a decent chair, a desk where the monitor and keyboard/mouse are at levels that are comfortable for you.

For software, something that plays nice with Linux.

For hardware, the M2 Air is a divine machine.

ThinkPad T430

pros:

• old
• extremely cheap
• usable performance, can be upgraded to average performance
• libreboot compatible
• very compatible with Linux
• great keyboard (if you mod it with a t420 keyboard)
• trackpoint (controversial)
• hot swappable batteries
• repairable
• display can be upgraded to IPS if you manage to find a converter board

cons:

• old
• bad battery life (if you keep the stock one)
• TN panel
• not blazing fast (more than enough for the tasks you mentioned though)

A second hand laptop like T430S

Here is a fantastic Google doc chart of good laptops and everything you would want to know about them that have an apu that is good for gaming without needing a dedicated gpu.

I would recommend the Acer Swift Edge 16, as it does pop up for $1,000 on sales, acer generally makes good laptops and don't have scummy things secretly baked in like Lenovo, has amd RDNA 3 apu for running stuff, and for future gaming while running Linux my gut says AMD apu will be better than Intel because Steam Deck and most certainly the future steam deck 2 use Linux with amd apu, so I think driver optimization under Linux or used alongside Wine will favor AMD.

https://docs.google.com/spreadsheets/u/0/d/1ap-mGyrNt723EO5v3B1nCW44R0XVMmOATpR-VZAXNgs/htmlview?pli=1

Maybe look into a used Thinkpad P series? They run Linux well, are typically more affordable than a new laptop which will definitely be 1K upwards, and have a 16 inch screen

Try a lenovo yoga ? Its small ,sleek and has touch screen , can be carried around easily !