The Nissan Path

Does anyone know if there were any models or trim levels that would be considered full time 4wd with an option for 4hi or 4low, but no 2wd option? I know the 4th gen 4runner v8 had that set up, but I don't know if the v6 Pathfinder had the same option.

All Pathys of this generation (R51 aka 05 thru 12) offer 4WD rather than AWD.

This is generally is taken to mean 2WD plus a 4WD mode (for many transfer cases in industry this also means 4Hi and 4 Lo as a choice)

In the Pathy some transfer cases in select trims (LE) had a "auto" option in their setting which is the closest to the "AWD" you are likely thinking of.
However even those transfer cases retained the 2WD setting as an option (and the most used setting for most on dry pavement)

^^ Very well said.

I keep my LE in AUTO mode almost all of the time, regardless of whether it's on dry or wet pavement. It's similar to the GM SmartTrak II in that it uses a wet clutch for the front driveshaft and can proportionately send power to the front wheels as need in a slip condition or when it anticipates a slip condition. I've noticed no gas mileage benefit when using the 2WD mode compared to the AUTO mode.