With the San Francisco 49ers roster essentially set it is a good time to review which positions are the best and worst heading into training camp. How should the position groups be ranked based on their depth and talent level? What is the San Francisco 49ers best position group? Linebacker There is talent at the top in Fred Warner, and the addition of Dre Greenlaw really helps. With young players like Jaden Dugger, Tatum Bethune, and Nick Martin, complemented by veterans such as Luke Gifford and Garrett Wallow, this is also a deep room.  Tackle Trent Williams is viewed as one of the best tackles in the NFL, and Colton McKivitz is slowly becoming one of the most underrated tackles in the NFL. Vederian Lowe is a solid swing tackle, Austen Pleasants made a start last year, and Enrique Cruz is a high upside bet. It is a solid room.  Quarterback  Brock Purdy is not quite one of the elite quarterbacks in the NFL like Williams and Warner are at their position. However, he is a quality starter.…