JP Gambatese had a Twitter thread on this but the best performing bottom sixes in the league are FLA, DAL and VGK, who get about 1/3rd of their goal scoring from those guys. Multiple conference finals, not to mention cup finals, for all of them. Our bottom six accounts for 1/4th. It is a problem and in the playoffs you need unsung heroes. I don't think the current group is capable of that.
The cap is what it is, you have to deal with it. You're trading a 50-60 pt d-man with middling defense to add 100+ points up front with that cap space. The team is good defensively and I'd argue that has far more to do with Keefe than the personnel playing in the bottom six.
Luke will have an uptick in points - his kind of luck always reverses itself. Nemec will be sheltered with Dillon and you can roll the other two pairs for 22 minutes a night.
If you take the empty nets out of it, we have lost quite a few one goal games. That extra jump up front is absolutely the difference. You can look at the latest game against Boston and how good things happen when you get the third line going and the top two lines still control play, even if they're cold at 5v5.