Okay. And the main risks are:

Too much powder, or too short of a COL, means too much pressure means blamy.
Too little powder, means they might not cycle the semi-auto, or will be squibs stuck in the barrel.
Too long of COL means they might not chamber or fit in the magazine.

Yeah, pretty much.

You can check for fit in mag and chamber before you go to the range, and you should.

Not cycling, or even squibs, isn't a big deal when you're doing load development. Only load a few rounds, watch for them, etc. No problem.

The "blamy" is the bigger issue, but honestly I don't worry too much about it as long as I'm playing with published data. I've only had one situation where I used published data (for a .357 Magnum load) and it seemed WAY too hot to be safe. I stopped using that load, and quickly.

You'll definitely see overlap if you look at multiple load data sources. Let's say that one book or website says that the range is from 5 to 6 grains, and another says 4.5 to 5.5. If I saw that, I would probably load a few at 4.5, a few at 4.8, a few at 5.1, etc. on up to 6 grains. At the range, I would start with the lowest and work my way up, noting any loads that didn't cycle the gun. I'd also be watching primers and cases for any signs of high pressure. For my pistol loads, I don't really worry about accuracy; I just want a load that will reliably cycle my guns while not playing too closely to the "max charge" line.