Welcome to the community @Martin_Neumann!
As n8n keeps always all the data of the workflow in memory will the SplitInBatches Node alone not have a positive impact on memory use. It is really required to split it up into different workflows for it to work.
If you work with large binary data, you can also try setting the environment variable N8N_DEFAULT_BINARY_DATA_MODE=filesystem. It will then save the binary data on disk rather than memory and DB and will so require much less RAM.