Syncthing is ok if you want to work on one project from multiple machines. I use Syncthing extensively for small projects and data sync across multiple machines and OSes and can recommend it.
But it has one disadvantage - you almost always need to reserve the space on both local machines on which you are working.
Lets say you have a 100GB project you want to access from 2 machines - you need 100GB space on every machine to host the data. Syncthing only checks if the data is synchronized.
There are write and read-only modes but they are not one-size-fits-all solution.
@cekuhnen have you considered rolling your own solution?
NAS builded on top of high performance hardware combined with dedicated software frontend (eg Nextcloud, OMV, TrueNAS) might be suitable.
With NAS you don’t need to worry about data duplication as you are literally accessing same directory from different machines.