Is a coward untrustworthy? how can cowards be tricksters?

A coward can usually be relied upon to try to avoid uncomfortable circumstances. Some cowards will lie, mislead, or flee in order to avoid unpleasantness, so some DO employ tricks and deceit. BUT there are also honest and forthright cowards. Just because one is cowardly doesn't necessarily mean one is untrustworthy.

no such thing as a coward just sensible people who logically balance risks and make decisions based on logic

Religious people are cowards. They can't admit that they may be wrong because their beliefs are unscientific.

Yes because someone who will not face challenges will also be deviously sneaky and deceitful to get away from them!