It’s just a matter of practice. One can work with Geometry, indexed BufferGeometry and non-indexed Buffergeometry
But Geometry is no longer recommended. See e.g. Will Geometry be deprecated or maintained along BufferGeometry?
In my addon THREEf.js I used all three possibilities in parallel. There you can compare well. But the thing there is quite complex.
Addon. Produces almost infinite many time-varying geometries with functions
https://github.com/hofk/THREEf.js/blob/b263d88d9b783b5dca4f5008e718997b6a3e75f0/THREEf_90/THREEf.js
There you can see what is achievable. https://hofk.de/main/threejs/sandboxthreef/
Maybe there’s something for you? https://github.com/hofk/THREEg.js