I think before making any scenario you should to read
SCS-DW_Mission EditorManual
Also good help is to check simple missions of other designers. Its because you sometimes ask for trivial things.
My scenarios are mostly for MP and are too complex for learning.
Check this awesome site:
SubGuru
Backing to question:
from my experience all tactics with search pattern are "aggresive". Also "barrier" tactic could give more autonomy to AI platforms.
"Transit search" tactic is less aggresive - AI works more carefully and doesn't engaging 5 seconds after enemy detection
For me "transit" is best tactic to keep AI movement quite stable. Warships are passive but still can respond to attack and defend themself.
it allows to make AI ship route in narrow straits or between small islands. (More aggresive tactics often ends running ship aground)
P.S. In RA 1.48 AI submarines are able to ping - i heard it sometimes.