This depends on so many factors that providing a definitive answer is impossible.
It largely depends on the project (complexity, ASIO load, etc.), the computer's power, and, most importantly, the quality of the drivers concerning DPC latency. Even a high-performance PC can struggle with real-time capabilities if the drivers are subpar.
With a good machine and reliable drivers, using the lowest buffer settings should pose no issue—though this applies only to specific use cases where it makes sense. For recording, you typically want to use larger buffers, even the maximum, to ensure stability.
Adding Steinberg System Link further complicates things by involving two separate systems and Steinberg system link on top of it.
Such scenarios need to be tested to determine what works. Perhaps someone already using Steinberg System Link can provide insights. However, this is not an RME-specific question.
That said, RME interfaces offer a solid foundation, but how well it performs with your system, projects, and Steinberg System Link remains uncertain.
It would be great to hear about the results of your experiments. I also suggest asking in the Steinberg forum to increase the chances of finding someone with relevant experience using RME or another brand.
BR Ramses - UFX III, 12Mic, XTC, ADI-2 Pro FS R BE, RayDAT, X10SRi-F, E5-1680v4, Win10Pro22H2, Cub14