I know in the past Anand has tested both review samples and retail chips with not much difference between them (see 8700K OC article) . They're also transparent about their testing methods in each article.
0.01V steps is fine if you want to get really close to the limits, but you'll probably want to start with something more coarse than that if you're going to begin at a conservative 1.3V. I'd recommend starting by upping the multi and let the mobo auto voltage give you a conservative starting point.
This guy got 5.1GHz @ 1.2V which is exactly what Anand got.
All 9700K CPUs have solder TIM, that's not something anand did. I assume True Copper as in; Thermalright True Copper (120mm tower cooler) which isn't exactly "exotic".
Also, cooling shouldn't affect the VOLTAGE at a specific frequency, only the maximum frequency achievable before you hit thermal limits.