The older office always allowed two install instances
Always only 1 (officially), assuming you ignore MAK and other volume options.
Retail versions were transferrable, thus you could uninstall from one machine and install on another, legally. MS' activation servers allow some element of grace on this on older (pre 365 era) versions, allowing a fair degree of use if you spead them out a bit, illegally of course.
OEM versions are not transferrable, and can only be fired once (or reinstalled on the same hardwareid). You could always phone MS claiming you had swapped out lots of hardware components, and could they reset it, but it seemed 50:50 if the agent would say that counted as a new PC, or reset it.
Newer versions use telemetry.
Many large companies are signed up to MS' HUP, granting active employees access to Office whilst still employed. What you are offered depends on the specifics of the company's agreements, but is usually either Office 2019 for around £15 one off, or a significant discount on the (in the process of being rebranded) Microsoft 365 subscriptions.
If you go for the former, if its offered, there seems to be nothing in place to disable the licence when you leave the company, or to disable it when you buy next year's offering for a 2nd PC. Though it is breaking the terms.
Office/Microsoft 365 subscription can be useful if you can adjust to the way it works, and store everything on Onedrive (but still maintain proper backups, obviously). But it also mains logging into your PC with your MS account (for it to be truly seemless). Being a luddite, I'm a foot in both camps person