3% and 5% are not code. They are Informational Notes to 210.19(A) and 215.2(A) — recommendations, not requirements, and an inspector cannot fail you on them alone. They are still what the drawings usually call for.
If you do upsize the ungrounded conductors for voltage drop, 250.122(B) says the equipment grounding conductor has to grow in the same proportion. That one is code.

Pick the type honestly — it decides the rule. The Table 220.47 receptacle factor (first 10 kVA at 100%, the rest at 50% — it was 220.44 before the 2023 code) is for receptacles only. Engineering software often puts it on every “power” load — saws, CNCs, chargers — which is how a drawing ends up showing far less than the code calculation.
Floor area: Table 220.42(A)'s VA/ft² already includes the 125% continuous factor, so it is compared with your fixtures at 125%, not multiplied again. Area is measured from the outside dimensions (220.5(C)).
Continuous = runs 3 hours or more (battery chargers, EV chargers, process heat): counted at 125%.
A multi-compressor RTU starts one compressor at a time. For the largest-motor and starting figures, the whole unit is conservative; enter the unit's largest compressor separately if you know it.
Not covered here: dwelling units (220.82–220.85), Table 220.45 lighting demand factors (warehouses, hotels), the optional methods for schools (220.86) and new restaurants (220.88), sizing an existing service from its demand record (220.87), fire pumps (Art. 695), and the neutral (220.61). All section numbers are the 2023 NEC.

This is how the Load Classification box on a Revit panel schedule gets its numbers, from the same loads: every load is HVAC, Power or Lighting. Types here map as HVAC = cooling, heating and HVAC fans; Lighting = lighting; Power = everything else. It is shown so you can reach the drawing's figure and see where it parts from the code — it is not a code calculation.

Standby (utility is the power, generator backs it up through a transfer switch) is sized to the full calculated load it can pick up — 702.4(B)(2)(a), unless load management sheds some.
Prime (the generator is the power — off-grid, generator + solar) is sized to the load that really runs. A stand-alone system may have less capacity than the calculated load, but never less than its largest single piece of equipment — 710.15(A). A measured peak is the best evidence of what runs: it is taken at 125%, plus whatever has been added since. Without one, prime falls back to the calculated load, which is conservative. A spot clamp reading is good evidence for sizing a prime set, but it is not a 220.87 demand record for a code calculation — that needs a year of demand data, or a 30-day recording in 15-minute intervals. ⚠ The 30-day route is not permitted once the service has solar, wind, or any peak shaving (220.87 Exception).
Solar does not shrink the generator unless batteries carry the peaks — at night and under cloud the generator carries everything alone. What solar changes is fuel and run hours; a diesel run lightly loaded at midday wet-stacks, so keep it above about 30% load.