I'm fond of how 5e is flexible enough and balanced enough around the encounters that if I have 1 or if I have 7, the PC's can feel a bit of a squeeze in each encounter. Multiple encounters tend to add to a feeling of struggle and fatigue, but even one encounter can be a potential party-killer.
I typically do a dungeon-style format, where I put 5-8 potential combats in for every expected long rest. These don't always turn into combats (sometimes the party avoids them or uses strategy to make them trivial or turns the kobolds into allies for a while or whatever), but that's the sort of the baseline or worst-case/most-fights scenario. I'll fill 10-12 locations with things, so we can fit in some empty places, some treasure, some places that are more puzzle-y, or some places that have allies, or some places that maybe rely more on skills and saving throws than on attack rolls (traps, hazards, etc.).
All that qualifies as one dungeon "floor" for me, and that's about how much I expect the group to be able to get through before they have a long rest. If they long rest before they've "completed the floor," there's usually some consequence to their narrative goals (ie: the enemies retreat with the McGuffin during the night because the party hurt their forces enough to cause a retreat).
I apply this format abstractly, so it applies to wilderness travel (a dangerous mountain they must pass through! A thick forest, full of dangers!), and also applies to more social or mental struggles (for a mystery adventure: the "floor" is a mystery they need to solve, with the "rooms" being clues that allow them to access the "exit" which is the whodunnit - long rest before you find out whodunnit and the perp goes into hiding somewhere else).
But I've run adventures with a more narrative-style format that is more like "OK, here's the ONE encounter you're going to have today!" and have enjoyed the results, too.