Arranging devices in rack cabinet

Here’s a list of devices we have so far, except (A) and (F), all other devices are on a wall-mount rack now, we’re moving all of them into a 42U rack cabinat.

(A) Server(5U) x 2
(B) Patch Panel (2U) x 3
(C) Stacked Switches (1U+1U+2U) x 1 set
(D) Another Stacked Switches (1U+1U) x 1 set
(E) Router, firewall (1U) x3
(F) Backup Tape Drive (2) x 1
(G) Cable Mamager (2U) x 4

What is the best way to arrange their location in the cabinet? Do I still need those cable manager?