So basically:
i7
8GB RAM to be expanded as needed
128GB flash drive
512GB external storage
Assuming that the operating system and your apps take up about 15GB, that leaves you a bit over 100GB as a workspace. Personally, I'd be more comfortable with 256GB, but 128GB is doable. The one point that I'd make is that I had an 11" MacBook Air several years ago, and while I loved it as a portable computer (it wasn't much bigger than an iPad), I felt that I was constantly fighting its 128GB flash storage limit. I just felt constrained, and I made sure that the next portable computer that I purchased had more.