Found this about the subject on reddit

In general, the 4-3 MLB is the largest and strongest of his unit, since his primary assignment is usually to stop the run, which often results in him being engaged with offensive linemen.

In the 3-4, one ILB is the "Ted", while the other is the "Mike." The Ted's job is typically similar to that of the 4-3 MLB's. He's most often use to get into the offensive line and take on blockers, which will then allow the 3-4 Mike, who is the more athletic of the two, to flow to the ball unimpeded (ideally, at least) and make the tackle.

It does vary from scheme to scheme, though. For example, the Tampa 2 MLB must be more athletic than most of his counterparts because he'll often find himself covering a deep zone between the safeties (which gives the scheme an almost Cover 3 Zone look) whereas a MLB in the traditional Cover 2 Zone will often find himself playing pass defense in a shallower zone (typically between his two OLBs).

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Yeah, I think the MLB and the "Ted" LB are basically the same and Campbell will be asked to fill it. While Walker will be the "Mike". Using the definition given above.

That being said, I thought the Mike was the MLB.

Also, I still think it's a crime to not throw in a surprise Tampa 2 coverage a couple of times per season when you have Walker. Maybe even less than once per game... but more than five times per season. Just as a surprise change up, you weren't expecting that now were you look.

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Different defenses have different terms on what they call the 3-4 middle linebackers....some call the strong side "Jack", some call it "Ted" and I am sure there are tons of other terms for strong side middle and weak side middle linebacker.

The reason so many offensive teams change strength is to screw around with defensive assignments. One can readily understand why MLF likes to run lots of motion (and a mystery to my why Rodgers did not like to run motion.)

It is.... in every 4-3. And one of them typically called Mike in the 3-4.