Choose a suitable board stack-up that supports 75-Ω single-ended trace and 100-Ω differential trace routing on the top layer of the board. This is typically done with a Layer-2 ground plane reference for the 100-Ω differential traces and a Layer-3 ground plane reference for the 75-Ω single-end traces.
Maintain a distance of at least five times the trace width between signal trace and ground reference if they are on the same layer. This prevents unwanted changes in the characteristic impedance.
Maintain a consistent ground plane reference for each high-speed trace from source to endpoint. Ground reference discontinuities lead to characteristic impedance mismatch.