Think his numbers are way better than Grays numbers to be honest mate, albeit he is a bit older.
As you say though, it's a big step up.
One thing I will say for Lewis Potter, is that he seems to score a lot of "scruffy" goals where he gets himself in the right positions between tbe posts. He doesnt look a player who had to rely on going past players easily to make an impact on a game.
More broadly, what I think Johnsons performance shows, is the importance of getting some experience in too. If as I suspect 2 of Gray, Richarlison & DCL leave, we will be losing experienced, pretty consistent players at PL level. That's fine to take a bit of a punt on 1 or 2 younger players, but we cant also be a soft touch at the back and lack leadership.
I'm not really a big pessimist in terms of relegation. Think last season was like a perfect storm of almost everything going wrong- world class manager leaving out of the blue, unpopular manager being appointed and ripping up structure, speight of injuries in all areas, new inexperienced manager only being appointed a day before games re-commenced and then a number of poor VAR decisions. I'm not sure we will ever get a season where they all go wrong again. And we still got 39 points in a league where typically 29-35 keeps you safe.
However, if we lose experienced players, and just add kids, we could very easily get sucked in again. Think if we can get a Tarkwoski and experience DM in, it probably puts a floor of 45 points on where we can finish, which is the most important thing.