Playing on a blind seed is the most fun (it's the way the game is intended to be played after all), but to get the best possible time and route for your run you will have to pre-scout! Here's how to do it without tedium or getting bored, while getting the most info out of your scouting run.
The map preview doesn't tell us much except the location of the main objective and rogue research station/illegal broadcast/escape pod (if present). Red splotches can be outposts or side objectives (including ones with no enemies, like SEAF artillery), while any non red spots can be empty terrain or POIs. Let's choose a chill landing spot, a scouting run should not be doing a hot drop. Behind extraction on the edge of the map is usually clear of enemies, but escape pod also works if it is present.
For loadout just pick whatever is convenient for you. I like to go with what I'm going to be bringing for the actual run just to get myself in the headspace of using my loadout, but it doesn't really matter
The first thing you should do on landing is to open your map, and possibly take a screenshot. You can already get a lot more info here than the map preview, although side objectives and POIs remain hidden
Don't worry about completing side objectives, just try to get them marked while exploring the map. Do complete any radar side objectives you come across however, since that will mark all side objectives and POIs for you, making your job easier. Pinging side objectives with q can mark them on your map as well (even from huge distances) but it does not work for every side objecive such as gunships, mortars, or AA guns. Your Helldiver will say "objective located" when pinging
Don't worry about clearing outposts, but do pass by and make note of the fabricator's location and orientation. This can help you setup a route later which includes long range fabricator snipes (big time saver). Also note how many medium and light ouposts there are (this can vary a lot heavily impacting your time!). The minimum is one medium and 0 light outposts for super helldive
For heavy outposts, make note of which kind they are, and their orientation relative to the rest of the map. There will always be two heavy outposts on super helldive difficulty
Make sure to pass by the main and subobjectives as well, since different variations can spawn which will have an effect on how you want to approach the map. This map spawned with the smaller air base variant, which I make note of
Since this is airbase, I note how many dropships are present on each of the objectives. Once you have your route planned out, it might also be worth it to do another scouting run to see where you can shoot them from, but for now you don't need to figure this out since you don't know how you will be approaching the map
2nd heavy outpost is the "tank factory" variant
It's also important to note what variant of a given subobjective has spawned in addition to their location on the map. For jammers, you can ping them with the scout passive to reveal if any fabricators are attached (the big red dots). This one does not have an attached fabricator (hard jammer)
Make sure to pay attention to how many mortars/AA guns there are when scouting this side objective, and where they can be shot from
And now the whole map is revealed to us, (except POIs because this map had no radar). It took me twelve minutes while making this guide, but I bet you can do it faster because you don't have to document every last thing with screenshots. Could potentially be done very fast with a mutiplayer party. Make sure you take a screenshot at this stage with the map open and clearly visible
When done, simply press alt+f4 (if solo or host). All other players can go back to their own ship (no need for non-host players to restart the game). Upon the host returning to their ship, the seed will have been saved in exactly the same state as before, ready to be speedrun. Now you can plan your perfect route to get the best possible time, just make sure to alt+f4 at the end of any practice runs (before boarding the pelican) to continue to be able to play on your map seed.