Anybody quoting that research as a reason not to play football may want to reconsider the research. It's poor research that's getting pushed around. Until we study the brains of most people who die, we won't really know. Remember, there was a recent study released that found CTE in individuals with no history of any type of collision sport....
As for the question about playing multiple sports, I'll stick with my philosophy I've shared before... Play as many sports as you want and DO NOT let a coach dictate what sports you play until they are paying you. Whether that's a club coach, high school coach, or a college coach.