How long does it take for plaque to form in your arteries? can 34 male with no family history and good stress echo consider himself less risky?

Only slightly: Arteriosclerotic plaques are not rare at your age. (A defining moment in coronary disease risk was the finding of coronary artery streaks and plaques in many healthy soldiers killed during the Korean War.) Your family history and good echo suggest slightly lower risk, but not nearly as important as modifiable risk factors like smoking, obesity, exercise, and lipid profile (cholesterol etc).

The most concerning: Plaques tend to take decades to get to the point where they create problems, which is why classic heart disease is so uncommon in 30 year olds. But remember the plaques start forming in childhood(fatty streaks) and progress from there based on your genetics and lifestyle habits/choices. While no family history and a reassuring stress are reassuring, it doesn't mean something isn't brewing!