Dula really dropped all the knowledge on this. I think the biggest issue is that you just have to let it grow. Like 0.001% of the population has whiskers that grows in nice. Everyone else's shit comes in patchy and uneven. You just have to live with it for a month or two. Just clean the neck every once in a while. I wouldn't even try to figure out the neckline, err on the side of it being further down.

Brush it constantly. After that grow-in period go to a pro to get the first trim, he can help establish the neck/check lines. Then just maintain from there.