Looking for Reliable Failover Set Up

[Ciclon_Industries]

First post and complete noob. Please reply like you would to an idiot.

We are in need of a failover setup capable of handling 5 to 6 Gbps traffic. Don't give a damn about the type of traffic. Reliability and redundancy are main priorities. Second one would be power consumption.

The following stuff is at no cost to us as we have it laying around: 

Several Ryzen 5 5900X
One Athlon 200GE (only used for flashing BIOS wen no BIOS flash button)   
Motherboards --> B450 Aorus M and a MSI X470 Tomahawk max.
500W and 750W PSU's.

If we were to get an Intel PCIe X550 NIC with a 10gbe port to receive. And then another Intel 4x 2.5gbe port NIC to send. Would that work as far as hardware compatibility with either the Ryzen or Athlon CPU running Opnsense? Alternatively we are open to suggestions.

Probably not relevant but here is our situation:


ISP is ATT and we have a 2g plan which actually measured 2.5G up and down - at least as measured via the ATT app. A few days ago we lost connection for about 20 hours and on top of that we have sporadic power outages. That led us to looking at 4G LTE hotspots that we could use as failovers. Which led us to T-mobile 5G home internet plans instead that we now have in addition to the 2G ATT fiber. Then all this led us to youtube videos on Pfsense. And then some random post on the internet about Opnsense led me here. 

So. 

We currently run several mining set ups consisting of a few GPU miners, 3x Dell R620 servers for threefold, an 80 TB storage rig for ScPrime, 2x helium antenna/miners, and some other nodes. It's difficult to say what these rigs combined will require in bandwith but I would say 1.5G when loaded is probable. If we decide to increase the size / number of rigs we can upgrade to the a 5 gig plan. If we can get about 600 to 800 Mbps with directional antennas wired into the T-mobile ARC gateway then close to 6g total. First idea was to buy a netgate appliance. Then we looked at the China appliances with the J4125 cpu's and 2.5gbpm ports.  And then we thought why not build our own since we have a lot of crap just laying around.