Dual WAN device to run OpenVPN and QoS

[Servance]

I hope you are all staying safe out there.

I need some advice. Currently the office has a 45/15Mbit connection and a Celeron based QNAP running OpenVPN configured as split-tunnel and this just isn't enough to support 10+ staff working from home. There are about 6 RDP (Home PC>OpenVPN>Office PC) and 5 staff who use the VPN to access shared drives on the QNAP directly.

The RDP connections run OK, but as soon as the users accessing the shared drives initiate a transfer the bandwidth is saturated and everything stops working.

There is no real server or RDP gateway and only select users can RDP. The router is a consumer "business" router which has no decent QoS. A 100/100 fibre connection is 3 months away and I need a solution before then.

The options are:

• Get another 45/15Mbit wired connection and run dual WAN
• 2 x 50/30Mbit 4G sims and run dual WAN (Draytek 2926L maybe?)
• fusionbroadband.com.au (mini-bonded product possibly but no idea of cost or if it even suits)

I need a device with enough power to run OpenVPN for 15-20 users, provide dual WAN and some sort of QoS so that when a file transfer is initiated it doesn't strangle everyone else. I don't know if load balancing would help, I was thinking it might be better to keep the WANs separate and put the RDP users on one and the Shared drive users on the other by designating IPs in the OpenVPN client files. There's a Win10 box that only services small SQL DB's with a Xeon in it that I could put OpenVPN on instead of the gateway device if that helps.

I have to set all this up remotely, I can't travel due to the Pandemic.
What would you do, and can you recommend a device/configuration?