In general - the problem with symbol size occur in AutoCAD and not in Civil3D. If Civil3D is available - Use Civil3D.
Starting with version 15.1.2 the installation for Geosuite Toolbox/Presentation delivered a GeoSuite default AutoCAD template. With this enabled, the symbol size will be correct. However, in later versions of AutoCAD there is a system variable introduced. This variable is not set in Geosuite Template because it must be able to support older versions of AutoCAD.
To solve this problem you can make a copy of the template that comes with the installation, change the settings to the desired values and save it at an appropriate place. You then refer to this Template from the settings file instead of the one that comes with the installation.
Read more about creating a custom template...
Configuration in Geosuite.ini
By specifying a template for the startup of AutoCAD may solve the problem with the symbol sizes.
To enable this feature, insert a new row into the [SYSTEM] part of the configuration file (Geosuite.ini)
(However, ensure that there is not already such a line - change in that case its contents as shown below)
ACADTEMPLATE=C:\Program Files (x86)\Trimble\Novapoint\GeoSuite\16\CAD\GSTemplate.dwt
Save the settings and restart Geosuite Toolbox.
The parameter PDMODE in AutoCAD controls how a “point” will appear. This should be set to 0. Unfortunately, it was set to 2 in the AutoCAD template that was sent with Geosuite. This is now corrected in later versions!