TV12 VPN speed - extremely sluggish and lagging

I read through an article about file transfer speedup in TV12. However, I can achieve not even remotely satisfying speeds, not in file transfer nor in VPN explorer file copy. Otherwise, the remote control speed is fine.

I'm trying to transfer file between 2 modern Win 10 computers ( less than 1 year old, one with an Intel quad core and the other with an intel dual core chip), with proven SMB/CIFS high speed performance in their respective LANs: a speed that can actually fully saturate their NICs 1Gbps bandwidth.
Internet connections are as follows:

computer in home 1: dual core: connected through a gigabit ethernet LAN NIC to a VDSL2 WAN connection (100mbps down/20 mbps up)

computer in home 2: quad core: connected through a gigabit ethernet LAN NIC to a fiber connection (1gbps down/200mbps up).

Trying to transfer from the home 2 pc (200mbps upload speed) to pc in home 1 (100mbps download speed), all I get in a VPN Windows explorer file copy session is an average download speed (according to infos displayed on the Windows explorer file transfer window) of 355KB/sec (2,77Mbps, 0.346MB/sec), against a theoretical top WAN tranfer speed of 100Mbps (12,5MB/sec). That's 1/36th of the maximum attainable WAN transfer speed. Incidentally, I tried VPN transfers between PCs connected on the same gigabit wired LA,N , and the speed achieved was roughly the same 355KB/sec speed I got in the WAN VPN transfer setup described above, which made me think that the TV VPN is kind of relayed.

Anyway, since I read that TV12 should allow up to 200MB/sec transfer speed (if computers and network allow it, of course), there surely must be something wrong either with my workflow or with TV12. Notice that, using Ookla speed test, I confirmed that all the WAN connections can transfer data at nearly their theoretical speeds.

Could someone help fixing this annoying issue?

Thank you in advance.