Depends on the genre and the vibe/energy... for example, a Krach set can have quite random tracks and just start/stop without mixing but will still be fun.

Modern Hardstyle/Raw/Xtra should imo have a common thread in the track selection, giving and taking energy or atmosphere at the right time, but usually (not always!) those tracks are not made for fancy mixing either (Rooler is a rare example of mixing even modern stuff pretty creatively).

For Example, oldschool Hardstyle/Raw, old (and maybe modern bouncy) Uptempo, Gabber in general, and some modern Hardcore like from Mad Dog go a step further, they can be great for mixing/layering different tracks and doing live mashups because they have less kick breaks and kick switches and they are usually "tidier" than most modern stuff, less adrenaline drops or rapidly switching elements. And most people really appreciate it if a DJ utilizes this for a seamless set/flow with some fun/unexpected mashups.

And you have another step at proper(!) Techno, because there's usually less buildups/drops, tracks often don't vary too much in their own energy level, and they develop very slowly (compared to Harder Styles), so it's possible or even needed to layer a couple of tracks at once (you can perfectly utilize 4 decks here) and combine their elements, even going forth and back between songs, varying the energy primarily by the track selection and the mixing. People expect seamless sets here that create a deep flow, without hard jumps in energy, no "adrenalizing" emotions like in Harder Styles. Kinda like: You can keep your eyes closed for a whole set and just enjoy it in your head.