So, this is mostly a film question but I use light meters with video also, but when do you use a spot meter as opposed to an incident meter or can you swap them. I've heard conflicting things about this.

Don't you use an incident meter when you can get in front of the subject and a spot meter when you can't or shouldn't?

is that the only difference? So technically, you can do without an incident and use a spot meter or vice versa? I hope that's the case.

A spot meter is a reflective meter. I used to use one on occasion to check reflectance off something that might be in the shadows too far away to go over and look at with an incident meter.

but technically, if it wasn't so far away, you could have used the incident meter to check the shadows and gotten the same results?

Yep. Assuming you read the meters properly. Any reflective meter is going to lie to you a bit--a dark surface reflects less light, so the reflective meter is going to say to open up more than you probably should, and vice versa for lighter surfaces. For example, if you took a reflective reading off a white card and shot what the meter said, the card would probably be underexposed, while a black card would be overexposed. If you hold an incident meter in front of either cards, it's going to read the same, and you would open up or stop down a little based on the film stock, the camera, the look you want. Both meters are guides to use in determining exposure. You don't always shoot exactly what the meter says.