Personally I would do this

Find an old laptop, desktop, any computer

Put proxmox on it. It’s free and lightweight

Create a Plex LXC. Also free and lightweight. There are community scripts to do this.

You should get pretty good performance on Plex, you can manage the computer through a web browser and it only costs you whatever the cost of finding some hardware to put it on is

I had a surface book at work about a decade ago. Honestly if apple came out with something like that I would maybe consider it. But compared to an iPad this will just feel bulky. And compared to a MacBook does the touchscreen even add anything?