How hard is migrating from one of the early branches to the latest one?

So, all I got is a couple of laptops (one of them running nvidia 9300m gs with 256MB and dx10, to give you an idea). What I want to do is build an older branch of UE4 from source (actually doing it right now) since they are less demanding on the hardware. Then, once I lay my hands on a more powerful machine, I want to migrate my game to the latest build. I don’t need blueprints as I will be doing gameplay programming in C++. Am I right in assuming that UE4 from 2014 will run smoother than UE4 from 2020? Will project migration be feasible, how radical have the changes been to the engine API for gameplay, animation (I am planning to do procedural animation)? Or is taking an early build about as good an idea as going with another engine altogether? PS Shader programming I will do once I migrate.