I think the most important thing in all of this is...
Klein or Kikaha will play Sam LB but they will only be 2 down players and see reduced roles. In a perfect world Anzalone/Davis will be your 1-2 punch in your Nickel Packages (60%) of snaps at the Will/Mike. In the event that Anzalone can't stay on the field you will likely see Davis at WLB and Klein at MLB in your Nickel Packages.
This is highlighted by DA saying that some of the LB's are practicing at a primary/secondary position. This is why Davis played some WLB at those Mini Camps and we already know Klein played Sam/Mike(In NIckel) last year.
Regardless the Sam will not play more than the slot DB - Robinson.
Klein's role will heavily depend on the health of Anzalone but he should definitely see fewer snaps than he did last year because he didn't perform well with the extended workload and it's pretty clear the coaches understand this as well.
If it were me I'd open up the season with Klein at Sam, Te'o at Mike, and Davis at Will on Base downs and then Use Anzalone as a sub package Will/Coverage LB until he proves he can stay healthy(Davis would kick over to Mike). Anzalone gets protected from the rigors of the run game while you also get your most experienced run defending LB's on the field on base downs.