There are a lot of points where RNGs are important.
Mapmaking. I start off with a very rough shape of a continent or island in Inkscape: eight to ten points defining the shore. Then I apply the "fractal" feature with a low depth setting. It breaks down each line into four randomized lines. I then move the one or other point if i see the need. Then it's a loop of fractal again, and another manual round until the shoreline is looking like I need it.
NPCs. I always have a list of names ready. Or to be more precise, a list of names for each relevant character race and population. On top of that, I have a list of roughly defined generic NPCs. Like "John Doe, male, baker, 34 years, married, two kids. Strong, enduring, but not overly smart." There are probably online generators for that, but I made my own back then. Just generate them by the dozens and pick those who you think are useful for the campaign. Whenever I use one of them, they get moved over to the campaign log.
More NPCs. I used a different kind of generator to create lineages and family trees. As always, generate a lot, and weed out anything that you don't like.