I want to get started as quick as possible and it seems torrenting is the fastest way, but I'm curious if I can then prune?
You can, but it seems you'd get the worst of all worlds:
- It's slower than letting Bitcoin Core download and validate simultaneously (as you need to wait until you have the full torrent before validation can start).
- It takes (temporarily) more space than just running a non-pruned node (as you're storing the torrent download + the Bitcoin Core data directory with a copy of the pruned blockchain).
- You end up with a pruned chain rather than a full chain.
If all you want is a pruned chain, run Bitcoin Core in pruned mode, and it will download, verify, and prune all simultaneously - never using more than a few GB of storage, and still faster than first using a torrent download.
Prune can happen but the client must still verify the chain from start to finish. Most devices are not limited by the download speed of the chain, it is usually to do with the verification of the transactions already created.