Ya echoing what Karateisland said, almost any module can be used for techno (except a blank panel).
Sequencers are (to me) some of the more idiosyncratic modules, and would be good to explore in depth those to get something that fits into your music-making approach/philosophy. There are specific sequencers for 303/acid, random + stochastic + turing machine, probabiltiy-based events, quantized vs unquantized pitches, menus vs. no menus, prescriptive, etc. Consider a handful of smaller sequencers that can be patched differently + synched depending on the day. Or a ‘battleship’ that does everything you’re after.
There’s also thinking about whether it is a studio instrument vs. live performance, or somewhere in the middle. How important is it to be able to change things on the fly, rhythmically, performatively, etc? If immediacy is important, that might steer you towards performance oriented modules.
Other have said this, and I agree, a mixer is an important aspect of techno production and performance. Once a patch is more/less up and running, the mixer becomes a key instrument. Things like hands-on mixers and sequencers with mutes, switches, wiggle-room, etc. Maybe an aux send is good to have in the case for being able to route sound sources to common effects and/or built-in saturation to ‘glue things together’.
Maybe start with identifying the most important types of sounds and dynamics you’re after. Dubby chords, glitchy textures, sidechained pumping sounds, specific drum kits, synthetic vs. organic and other false (yet useful) dichotomies. Clean, cold, distorted, warm, aggressive, smooth etc. Absolutely find a way to create your favorite drum sounds, especially a kick drum or three that sounds perfect.
OK if you’re still reading, definitely check out some artists making these sounds w/ modular like Steevio, Surgeon, Aphex (good luck!), Julia Bondar, Mylar Melodies, Baseck, Trovarsi, dc11 (Lucas Marchal), Spring Rolls (Bastien). Most of these folks have detailed videos/feeds with examples of sounds + modules employed.
Have fun!