LGS file is a Leica format, it does much of the same things as an e57, but they are build to be consumed by Leica software and plugins. LGS is a format that includes a boat load of extra information, and is made to work efficiently with leica's tools, but if you don't have the tools (cloudworx, jetstream, cyclone), you are limited in ways for clients to consume the data. LGS is a registration in a box almost, where your scans, 'assets', and 360 photos are included in the 1 LGS file.
Archicad is a BIM software and not a pointcloud software. It is possible to import pointcloud through xyz and e57 files. Archicad translate a pointcloud into a GDL object you are able to find by a LCF file into your local documents.
If you recieve a heavy LGS file you can imagine it will not be a "ready to use" file because it's not an open file format and it is a too heavy file to be used into. a BIM modeler.
I invite you use CloudCompare to open these kind of files :
Cloudcompare is a awesome freeware for Windows, MacOS and Linux :
I always use this freeware to divide by 10 the weight of my files before importing them into Archicad (without loosing important information of course).
Christophe - FRANCE
Archicad Designer and Teacher
Archicad 15 to 23 FRA FULL
"Quality is never an accident; it's always the result of an intelligent effort " - John Ruskin