Mac has mega slow SMB connection. VMWareFusion Windows 10 has mega fast SMB connection, same Mac

I desperatly wanted Apple to answer my request and fix it but after being on support for 2 hours I stopped as they were totally useless.

My set up is VPN connection into the Synology NAS in the office from my Mac via SMB3. Mac is a 2019 iMac so not slow.

Office network is brand new Cat7, Gbit ethernet

Upload/Download speeds from ISP are as fast as you can get at both ends and there is no throttling on the NAS or router.

It is unuseable as its so slow, it takes 10 minutes to open a folder let alone try and work from InDesign.

Here is the hard part to understand.

I have VMware Fusion with Windows 10 on the same Mac using a bridged network connection.

If i use the same VPN connection connected through Windows 10 its blisteringly fast, its like being in the office, I can work like im in the office, only a very slight lagg on saving.

I have turned off packet signing on the Mac, made zero difference.

We are about move all the home Macs (12) to PC's as we cant run the business like this.

Any help would be really appreciated