Advanced stats have come a long ways... Corsi is very primitive and misleading at this point. Plenty of players out there that have good Corsi numbers, but poor overall numbers.
For all the talk of Byram being a legit #1D, we really need to see him put it all together. 10 years ago, you could reasonably say a 40 point guy who played great defense was a #1. Today, that threshold has to be closer to 50 points with scoring being up as much as it is, especially for defensemen. Then those guys who are at that 50 point level or a touch below, they have to be elite defensively. We have not seen Byram be able to pull off both consistently.
On offense, we can see him activate and create chances. When he's trying to push offensively, he clearly has the ability to drive some chances... and you'll see the production follow. He can have a 10-15 game stretch where he is near PPG. The problem becomes that he is very much a trade chances guy when he's like this. The numbers actually state to a worse extent than Barrie was in his prime (IE not ideal). Part of that is how he creates offense. He's not the most versatile in his attack. This will sound harsher than I mean it, but compared to other high end D... he's not a great outlet passer nor is he a high end rusher of the puck. He's somewhere between above average and good in those areas. So it isn't a weakness, he's just not going to be able to pile up points like Hughes does in those areas. Where Byram's offense comes from is activation. Using his skating ability to be another option off the rush. Either the 3rd guy in on a 2 on 1 or 2 on 2.... or as the 4th forward so to speak. This creates mismatches and ability to score on the counterattack. His other activation is taking risks in the offensive zone. He will read and go to soft spots to get quick shots or one touch passes. Those are his main two weapons offensively. They will produce, they'll just be a bit erratic in ups and downs. Also this activation provides counter attack possibilities, which teams really took advantage of last season. You could clearly see that once they broke up the play, they could practically get a free zone entry... and either trade chances off rushes or pin the Avs after an entry.
Which brings us to defense. I've said for a long time that Byram has elite 1v1 defensive skill set. His size, skating, stick, physicality, etc... it is all tailor made to be an elite 1v1 defender. When he is keyed in and focused on that, he is incredibly good that way. He's not always keyed in and focused on it. When in position (the activation thing), he's fantastic at zone entry denials. He's also fantastic at containing a guy within the zone when he's covering the puck. Where Byram has lapses is within space. He loses his coverage pretty quickly. He chases the puck when it is near. When he retrieves the puck and is collapsed upon, his default is skate with the puck that frequently causes a turnover or puck battle or put it behind the net for his partner. This all leads to extended zone time pressure. Two types of teams give him absolute fits... the heavy forecheck that eliminate space. Those teams also tend to be heavy in the zone and cycle the puck decently. Then the teams that have a good amount of skill and rely on passing and movement in the offensive zone. I'm not sure he will ever fully get past those two issues. The heavy teams specifically will be hard to overcome. Practically you need a bigger cycle buster to work with him, but one who doesn't handle the puck like a hot potato (Manson in his prime would have been absolutely perfect... or Tanev in his prime). The space teams can be mitigated staying more engaged... at this point it is hard to see that fully going away (tends to be a sticky issue).
What I personally think should happen with Byram is having the reigns pulled back on his activating. Really key him in as an elite 1v1 guy. Tone down the tradeoff chances and stay in better positioning to break up plays off the rush or quickly 1v1 in the defensive zone. This will lead to less extended time in his own end and less reliance on his partner moving the puck quickly. As the Avs have started to do, play more man defense with him and have him attack defensively instead of staying stagnate. Tone down the activation and make it smarter... IE don't join as a 4th guy on a 3v3, sometimes even a 3v2. Don't activate down from the point on the backdoor nearly every time giving up an easy exit for a team. Stay higher in the zone. Attack more in the neutral zone and on the blue line. Hold back the attack at all costs mentality. When he has the games where he does that, you see his defensive numbers and impact massively improve to the point where I'd comfortably say they are high end. His offense takes a hit though. He doesn't produce like a 45 point player... more like a 30-35 point guy, but the GF% tilts rather dramatically.
I'd rather have the less flashy and less points, but very solid defensive guy than a trade chances guy who puts up 45-50 points. More Ryan McDonagh and less Keith Yandle. I know it isn't popular to pull him (or any player back), but it is smarter hockey at this level. He isn't a Makar type of guy, nor does he need to be.