Old school IGS file will be smaller than Parasolid. Also in Mastercam, if you save all solids as wireframe and surfaces. The file will be smaller. But , I do prefer to work with solids.

I did not know that, thank you. But if you have both of them, the file will be bigger

Sometimes the levels get full of copious entities or some other throw away data, if you move all the geometry off the level, and it is not empty, select the level and hit the delete key to free up memory..

Surfaces actual take up less room than solids.

YUP RANDOM FILE GROWING WITH NO CHANCE OF SHRINKING THEM BEEN GOING ON WITH US SINCE 2021. Many threads on the Mastercam form about it. My work around is if I see it growing I save all solids I need as STP then open a new Mastercam file import STP models and start over! If you allready have toolpaths you can export them then import to new file, Seriously a real PITA!!!!

The issue with converting planes to surfaces in MC2023 has been communicated to us (and logged as R-31173). Those should not be getting created. That is not corrected (yet???) in a 2023 update though. History? If you imported the solids history (and it sounds like you imported the wireframe edges too) then those settings will definitely affect file size. But basically, there's really no correlation between the size of a SolidWorks file and the size of a Mastercam file made from that SolidWorks file. Mastercam carries non-model-related information in its part files (planes, levels, maybe machine information, etc) that will affect size ... and so does SolidWorks.