The demarcation lines
33 CFR Part 80 draws the line between Inland and Near-Coastal waters — typically a line across harbour entrances, sound mouths, and bay openings. Outside these lines, COLREGs applies; inside, the Inland Rules apply.
Two parallel rule sets
COLREGs (International) and the Inland Rules (33 CFR Part 83) are largely identical, with several known divergences (Rule 9 narrow channels, Rule 10 traffic schemes vs VTS, Rule 24 towing, Rule 28 constrained-by-draft, and Rule 34 manoeuvring signals as 'intent' vs 'action').
Which to choose
If you'll operate inside the lines (lake or bay charter), OUPV Inland is enough. If you'll fish canyons, run further offshore, or operate on the open ocean coast, you want Near-Coastal.