Can I replace the internal SSD in my Amber X with a higher capacity drive?
No. The Amber X form factor was engineered for a compact footprint. There is complex circuitry with flexible materials, along with thermal pads that greatly increase the chances of a short circuit if internal modifications are made.
To expand your storage capacity, simply use an external SSD/HDD and save away! Please view this article on how to expand the storage on your Amber X.