I would set it up in terms of workflow. My work order is: paper safe -> paper cutter -> enlarger -> chemicals -> sink -> drying area. That ends up being about a 270-degree circular rotation, for me: my darkroom is in the older of our two kitchens, so I was kind of pinned in by a sink. I built the arrangement around that...so, don't confine yourself to C-shapes, or I-shapes, or L-shapes. Just get started working and move things around as you need to do so...it won't be in a "final" configuration for a long, long time. There's no best layout...just the best for you. My layout is sort of an L-shape, with my medium-format enlarger occupying the empty corner of that arrangement...it works great for me. Experiment. See what happens.