Looks? I build giant boxes and put giant automation in them. I can’t be bothered to make giant box look nice when I got my factory to automate!
I play with the best graphics the device I’m playing on can support with a reasonable frame rate, but that’s never come at the cost of functionality. It’s usually fps vs graphics, not functionality vs graphics.
For me form comes before function quite often in that I’ll build the contraptions first, but I’ll build them with a build or exterior in mind so by the end it’s a good balance.
I’ll usually try to do both, but if it’s not possible, function has higher priority.
A bit of both.
I don’t typically build things just for the looks, but once I’m building them I take aesthetics into account. Just the usual - picking a style that fits what I’m building (e.g. cottagecore for villager-powered farms, industrial for Thermal mods, steampunk for Create etc.), design the thing in creative mode, then build something that fits the terrain OK to host my contraption.