I would not recommend logging into my personal Apple account on any devices owned by my employer.
You very likely signed an inventions assignment at the beginning of your employment, where everything happening on work time or on work equipment is assigned to your employer. (This may not be as ubiquitous outside the US, though). For example, my last three employers had PhotoStructure on file as a "prior invention" that I owned and declared.
Depending on how litigious your employer is, your photos, videos, and documents on their devices could certainly be retained and ownership rights granted to them.
Keep work docs and source off of your hardware, too.
