You’re picking the harder path mane but there’s fun in that too. Get bigger and stronger everywhere (srs… everywhere) and prioritise back to balance out your physique.
For back focus on progressively overloading not just the weight but volume etc. Keep deadlifting, add in vertical and horizontal pulling variations that you like and progress all of them. ez
Diet too. Will probably need a good massing phase in you before thinking of anything else so just eat big consistently and you’ll grow.
Not all relevant but some others and me wrote some useful points in this thread: