Is this possible with bcoin? Do I need a full node to get transactions or does it work with an SPV?
SPV node watches your addresses on network broadcasts. So on SPV Nodes you won't be able to grab other transactions then your address. It communicates with other peers, fetches your transactions using bloom filters and then watches pool broadcasted transactions. So you only get transactions that are addressed to your wallet.
With fullnode, there are two places bcoin looks for tx:
Bcoin will always return transactions from mempool.
If you want to get transactions from chain, either by address or by transaction Hash, you need to enable indexing:
You can check
RPC docs: RPC-Docs