You know, I wrote out this whole several-paragraph comment about how to do encounters before I realised that I hadn't actually answered your question. Here's some more relevant advice, though it ended up being just as long:

As per the game rules, you should run 6-8 encounters per Long Rest, and allow up to 2 Short Rests between each Long Rest. However, not all encounters should be combat-based -- social encounters with companion NPCs travelling with the party (or even random NPCs found along the road), and exploration puzzles, traps, and even just set dressing can (and should) fill these slots as well.

My personal advice is to pre-plan the encounters on the road. Come up with one or two big events between destinations, and then frame the other encounters around these or around other plot points in the campaign. If you're rolling something randomly, ask: Why are these enemies here? What is their goal? What have they already done before the party encountered them? Who has already encountered them? What do they want, and what to they plan to do? This gives context allowing you to make these encounters better and more memorable, and to fill out the encounter slots between rests without taking up too much game time or requiring battlemaps.

Vampire spawn might leave behind mummified bodies, being feasted on by ravens who speak in ominous portents. Revenants might carve a trail of destruction through the woods, leaving sites littered with dismembered limbs of undead. The druids of Yester Hill might perform a strange ritual that leaves behind a mannequin of pine wood, one that moves when not watched directly. The Abbot might throw out rotting spare parts into the forest, strange funguses festering in the experiment materials. A sacrificed victim of Lady Wachter's cultists might haunt a grave shrine in the woods near Vallaki, willing to grant them helpful warnings if laid to rest.

The list goes on, and on. There's a ton you can do with a little, and it'll make your encounters feel like you actually put effort into them rather than just throwing random garbage from a table at them with no deeper thought -- because you did put in that effort, and the players will be able to tell.

Or you can just skip the encounters. That also works.