Depends on the context but,「まあ」can sound very casual and used more in a verbal communication.
In writing, one basic principle is「です & ます」to be not mixed with「である」in one writing.
「もの」is for tangible things「こと」is for intangible things, activities and ideas.
「地球の環境を汚染から救えます」”We can save earth’s environment from pollution.”