Surely McKenzie will be on Johnson. Johnson is much more physical then Housh. McKenzie is a significantly better matchup with him. I believe Johnson is anticipating this with his compliments.
And as for McKenzie. Look when we got him he was one of the top CBs in the NFL. The change in rule emphasis hindered his physical style (which is why he draws penalties sometimes) but it's not like he turned into a pumpkin. He still has cover skills.
CBs get way to much criticism considering the difficulty of the position and rarity of talent. I guess that's why they are always so weird and crazy.