Double vanity shared P-Trap
The &quot;point&quot; (as is so often the case with plumbing code) is not causing a situation where the drainage from the sink with the longer arm to the trap causes the trap to siphon dry and let sewer gas into the house.
Since the drain-holes are 30&quot; apart, that's allowable. If they are more, it's not. Welcome to code compliance.
If &quot;more storage&quot; is your watchword, you could run two traps towards the rear of the cabinet and put the crossing pipe to the drain closer to the back wall of the cabinet, freeing up all the space between the drains currently blocked by the crossing pipe.
Slope is 1/4&quot; per foot, as usual for &quot;smallish&quot; drain pipes. IPC states that as minimum slope for 2-1/2&quot; or smaller pipe size. UPC is probably similar. Tape a 1/8&quot; block to one end of your 6&quot; level and look for level to check that.