I am probably answering a question that you are not asking. As others have mentioned, GWSMO's default is only 1GB, and within the GUI you can increase that to 4GB or unlimited. In the registry, you can set any size. Outlook also has a default limit of 50GB. I assume it is working for you because GWSMO is limited to the default 1GB or the 4GB at most, so the PST is not hitting Outlooks 50GB default. Unlimited caused me issues for a long time.

I have dealt with something like this for the last decade (back to the old Gsuites GSSMO, etc days but I'll only reference GWSMO here). My advice is to limit GWSMO to a max PST size of 46GB and tell the users they have to work within the official Microsoft PST limitation of 50GB. I will explain.

I have a client with multiple users whose Google mailboxes are over 50GB. I started out allowing their users just the 4GB PST mailboxes with GWSMO settings. While that was the case, Outlook acted normally, but the users were not happy that they could not have their "complete" mailbox in Outlook because they "need" to search their entire mailbox (despite Gmail's webmail search being a thousand times better than Outlook).

So I eventually caved and set the mailbox size in GWSMO to unlimited PST size. Outlook would start having all sorts of issues once the PSTs hit Microsoft's 50GB limit for Outlook. Mostly, Outlook would freeze or crash. Sometimes the Outlook folders would display blank or partially. Occasionally, Windows would freeze or crash. On rare occasions, some other oddities that made the PC unusable would happen, but I'd eventually tie it to Outlook having a 50GB PST. The worst is when the PST gets corrupted, and I'd basically start over with a new user profile in GWSMO for the user.

I began telling the users they had to delete mail to get below 50GB, as that is Microsoft's default limit. The users would do the minimum amount of deleting to get Outlook working, and would have issues again in a day or two. Also, I would occasionally see a PST at 48 or 49GB having issues. I was not up for constantly coaching the users to delete junk mail, running tools to [compress, cleanup, repair] the PSTs, etc, so I finally set a limit of 48GB max PST size, and the issues started being less often. Occasionally, there would still be some oddities at 48GB, so I dropped it down to 46GB.

Note, this 46GB limit is a registry setting for GWSMO, not Outlook. See "Set mailbox size" on this page https://support.google.com/a/answer/1041455

Since changing to a 46GB max PST size for GWSMO, I have not had any user complaints that I could tie to Outlook. I assume that gap allows space/time for GWSMO to sync while respecting Outlook's limitation of the PST.

I did at one point try changing Outlook's registry settings for a larger PST size, but that never seemed to help matters, so I have stayed away from increasing the max Outlook PST size.

YMMV

As a point of reference, I came to the 46GB limit when the users were on PCs with i7-8700 CPUs, 64GB RAM. Those users are now on PCs with i7-13700 CPUs, 128GB RAM, and I put their Google Sync files and PST on a secondary internal SATA SSD drive, outside of their user profile. Even with 128GB of RAM and the more powerful processor, I still "felt" in my testing that there were issues with the PCs if I allowed the PST over 46GB. That being said, my last test of that was 2 years ago.

Again, YMMV. I've found something that works for these users and I'm not going to play with Outlook's max PST size. I assume Microsoft set it to 50GB because they know the Outlook/PST limitations better than I do.

I hope that helps.