Could expresses an idea, option or solution for someone else to take. Could leaves the decision making to the other person.
Should expresses an opinion about an action we think is smart for someone else to take. Should expresses advice about what is "good" to do and is influenced by my background, my mood, my feelings, my triggers, my prejudices, and my expectations and am projecting them onto someone else. It is used to influence or affect the other person's decision-making.
The Bible says, “The fear of man bringeth a snare: but whoso putteth his trust in the Lord shall be safe.” Proverbs 29:25
“Truth is different from belief. It is different from hope. Absolute truth is not dependent upon public opinion or popularity. Polls cannot sway it. Not even the inexhaustible authority of celebrity endorsement can change it.” - Elder Dieter F Uchtdorf
How many times have you gotten a “should” and you were excited about it and acted immediately? That’s because shoulds also sound like guilt trips.
