Regarding to 2D and 3D, please refer this link https://optics.ansys.com/hc/en-us/articles/360034914633-FDTD-solver 2D will lost some field components since the 3rd dimension is considered to be infinite.
In general, using 2D simulation can get quick insight for some physics. But it is better to use 3D since real device is 3D. If 3D is too heavy to have a quick simulation, you can use varFDTD which uses 3rd dimension informaiton but simulate in 2D (thus 2.5D). We suggest to use 3D simulation for final verification.
You should be able to get the visualized result, Please refer https://optics.ansys.com/hc/en-us/articles/360034922953-Optimization-utility
If not, you can right click the optimization and load the result:
You can also use script to see which result can be obtained:
For example, if you want to get bestFom, you can use
Please refer this link https://optics.ansys.com/hc/en-us/articles/360034409814-getsweepresult-Script-command
getsweepresult outputs dataset, whereas getsweepdata gives the numerical values.