Guitars with an internal preamp are much less critical regarding load impedance. A peizo pickup in most cases always uses a preamp because it requires an even higher load impedance than an inductive pickup.
Jensen Transformers (USA) make an excellent but costly DI transformer.
https://www.electro-tech-online.com/custompdfs/2009/04/as066-2.pdf
If you are running Bass guitar through your DI it is important to select a transformer that will handle high level low frequency signals without being driven into saturation and causing distortion. Some small audio transformers
perform badly with Bass for this reason.