Is there any way to know this is legit?

OpenWRT is basically Linux for routers and can be installed on a variety of devices - https://openwrt.org/

There is also https://www.gargoyle-router.com/

Yes, do the S3 integration before moving, for sure.

Oh right, yeah, Wordpress does tend to use up an awful lot of storage - every image gets copied 5 or 6 times, in different sizes just incase you need that size. It’s nuts.

You don’t need to store those images in your server though, they can be uploaded to S3 (object storage) where it is 10x cheaper to store them and then you can have a cheaper VPS. This way the VPS only needs to have enough storage for your MySQL database.

https://wordpress.org/plugins/amazon-s3-and-cloudfront/

There are many providers of S3-compatible storage, you don’t need to use AWS. Cloudflare R2 is super cheap - https://www.cloudflare.com/en-gb/developer-platform/products/r2/ or Hetzner - https://www.hetzner.com/storage/object-storage/

This is good advise, listen to dan. WP Super Cache is amazing although getting it working just right can take some tweaking.

The Redis Object Cache plugin is worth a try. It’ll only take a minute to set up.

Is it 200k users or 200k page loads? Those are really different as each user will load multiple pages in a month. If it’s 200k page loads then that server is way way too powerful (and expensive). Don’t let a crappy developer hide their lack of optimization skills by throwing your money at the problem.

It exists and I’ve tried it - https://en.wikipedia.org/wiki/Davfs2

Thing is, when an app thinks a directory is on a local disk, it does things which do not scale well over a network. e.g. reading every file in the directory to make thumbnails.