Taking the times 7:00 to 10:00 inclusive - too long time for your specific plans, but gives a more consistent and understandable picture to figure out and memorize the patterns
G:
Shanghai-Nanjing:
G7002 7:00 1:38
G7036 7:13 2:05
G7004 8:00 1:33
G7038 8:05 1:56
G7040 8:16 1:58
G7042 8:25 2:07
G7044 8:52 1:58
G7006 9:00 1:19
G7046 9:20 1:58
G7008 10:00 1:38
Pattern here: G700x at sharp hours, 1:19 or 1:33...1:38, G703x-704x at random times, 1:56 to 2:07
Hongqiao-Nanjing:
G7122 7:35 2:03
G7382 9:03 2:05
G7124 9:15 1:58
Pattern here: few trains, random times, 1:58 to 2:05
For comparison, times to Nanjing South:
Hongqiao-Nanjing South:
G102 7:00 1:13
G222 7:05 1:14
G104 7:10 1:21
G106 7:15 1:21
G108 7:53 1:19
G12 8:00 1:07
G110 8:05 1:21
G32 8:17 1:14
G34 8:45 1:27
G2 9:00 1:07
G112 9:05 1:19
G36 9:15 1:21
G114 9:27 1:21
G230 9:39 1:14
G116 9:45 1:14
G14 10:00 1:07
Pattern here: random times, but all from 1:07 to 1:27 - from Shanghai, only G7006 compares
Shanghai-Nanjing South
G7232 9:35 1:54
Pattern - only one train, and no advantage.