I want two laptops in one body

Couldn't this be accomplished with a hypervisor and 2 virtual machines?

I don't know how practical this is on Apple hardware (I don't deal with hardware much overall, I'm a software guy), but in general, you can usually get by with just two SSDs/HDDs, each with a different OS instance on it, to separate work and home. Assuming, of course, your company would allow you to modify your work machine, if they gave it to you. A physical switch is pretty unnecessary, as you couldn't switch between systems without cutting power to one anyway (and basically nothing is stored outside the hard drives anyway); choosing a drive/OS on boot should be fine.

How about carrying an USB-C SSD with VMs on it? You can have however many switches you want, not just one.

One answer is to have the work "laptop" be a cloud desktop. This is a popular choice for firms (say the Bridgewater hedge fund) that are paranoid about computers falling into the wrong hands.

Keep in mind that many employment contracts and much labour law considers work performed on the employer's equipment to be the property of the employer.

Technically, a hard-drive swap would address most of your concerns. (There remain risks of hardware / bios keyloggers and other surveillance tools.)

Either get a cheap notebook for yourself, or leave the work box at work, and explain your rationale.

Dual boot?

duct tape

I had a second hard drive attached to the side of my laptop and ran it in a virtual machine that is the closest I have gotten.

I use two different logins. One is my "Writing Room" with no access to the internet or...the internet. Just Sublime.

The other login is all the stuff and work.

I like the Writing Room.

Multiple user accounts/logins. You can move one or more of the /user folders to an separate disk if you want.

you want one physical computer with two logical computers - dual boot.