So a straight razor is the old fashioned, flip out single blade, need to sharpen kind. Not sure if you're intending to refer to that or not. Whereas safety razors are the two-sided head cheap disposable blade kind.

I can't talk too much about straight razors, I think they're a bit dangerous without a good amount of practice.

Safety razors are fine for below jawline shaving, though you will probably nick yourself a bit until used to it. I use a Merkur 25C and have a beard and I think it's excellent. Rarely nick myself. Could never use electrics or modern disposables effectively, they tended to load up and clog badly.

For what it’s worth I did this for years, without issue. It’s perhaps a little slower, but not much when you are just cleaning up. It takes a little practice to get good at maintaining the line, and you do need to care for the blade (not a lot of time, but required).

At first you will be slow, as worried about cutting yourself. You probably won’t actually cut yourself until you relax about it after while...

You won't cut yourself if you keep your razor sharp and use good technique. Short, confident strokes with your other hand adding tension to your skin. Really I rarely cut myself with a straight razor now. And it's usually because the blade starts getting dull, which happens after like 6 months.

What an approach to pulling a literally razor sharp blade across your own neck.. “be confident”.