The intended design of Syncotec synthetics is, ultimately, secondary to what your group thinks is cool. There is no specific mention of physical chassis descriptions cause you can aesthetically be either Wall-E or Detroit: Become Human with no real bearing on mechanics. It's really up to what you'd prefer and what fits your game.
If you want a "canon" aesthetic, Syncotec synthetics are Star Trek, H&B are D:BH, Westeki are XCOM's ADVENT, and ALaRM are Star Wars. But again, there's nothing mechanically stopping you from going crazy with it. They all make synthetics with a range of appearances, those are just the stereotypical looks.
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Archetypes/quickstart builds could be useful, I'll look into that. Starting with gear probably wouldn't break the game, but can effectively be achieved via your Jumpstart. Plus, starting with gear is an advancement, so after your first mission you can pretty easily grab that in-built SMG