current distribution in microstrip line -ieee

Waveport is usually the best, lumped port is used primarily when you need to put a port inside the structure

Also check the current distribution, especially important in edge coupled lines. See the mesh refinement pictures I posted here:

https://www.edaboard.com/viewtopic.php?t=115680

If you lower Delta_S below the default 2% you must also lower the port refinement along with it or your normalized S-parameters will be inaccurate since calculated Z0 is inaccurate.