Strange Brigade in DX12 mode does not use multiple GPU. It seems to want to use multiple GPU when launched in Vulkan mode.
But then, my case, with one AMG and one nVidia, it freezes when wanting to start the game.
I think you better check up on this, pretty sure there's mGPU support, or CrossFire support at the very least. When I was playing with just one VEGA64 on my monitor at 3840x1080, I recall getting about 70fps - 110fps, but now with two cards, I get about 140fps to 200fps, very good mGPU scaling actually.
I just recall I did save my benchmark runs on Strange Brigade:
Single VEGA64
Strange Brigade Benchmark Report
================================
Created: 2018-11-29 at 20:40:22
Build Version: 1.47.22.14 D3D12
================================
Average FPS: 69.8
Minimum FPS: 51.7
Maximum FPS: 90.5
Number Of Frames: 4191
Total time: 60.0s
Average Frame: 14.318ms
Minimum Frame: 11.044ms
Maximum Frame: 19.354ms
1st Percentile: 11.552ms
3rd Percentile: 11.859ms
5th Percentile: 12.026ms
95th Percentile: 17.166ms
97th Percentile: 17.460ms
99th Percentile: 18.259ms
Machine Name: 3960XTREMEPC
CPU Name: Intel(R) Core(TM) i7-3960X CPU @ 3.30GHz
System RAM: 16324MB
Number of Cores: 12
GPU Name: Radeon RX Vega
Number of GPUs: 1
API: D3D12
API Driver: 25.20.14011.5005
Dedicated VRAM: 8120MB
Monitors: 1
Output HDR: ON
Display Width: 3840
Display Height: 1080
Render Scale: 1.00
Render Width: 3840
Render Height: 1080
Texture Detail: ULTRA
Shadows Detail: ULTRA
Draw Distance: ULTRA
Anti-aliasing: ULTRA
Anisotropic Level: 16
Tessellation: ON
Ambient Occlusion: ON
Obscurance Fields: ON
Motion Blur: ON
Vertical Sync: OFF
Reduce Mouse Lag: OFF
Dual RX VAGE64's
Strange Brigade Benchmark Report
================================
Created: 2019-02-18 at 22:45:06
Build Version: 1.47.22.14 D3D12
================================
Average FPS: 150.1
Minimum FPS: 44.5
Maximum FPS: 277.7
Number Of Frames: 9009
Total time: 60.0s
Average Frame: 6.660ms
Minimum Frame: 3.602ms
Maximum Frame: 22.460ms
1st Percentile: 4.953ms
3rd Percentile: 5.270ms
5th Percentile: 5.374ms
95th Percentile: 8.472ms
97th Percentile: 8.778ms
99th Percentile: 10.031ms
Machine Name: 3960XTREMEPC
CPU Name: Intel(R) Core(TM) i7-3960X CPU @ 3.30GHz
System RAM: 16324MB
Number of Cores: 12
GPU Name: Radeon RX Vega
Number of GPUs: 2
API: D3D12
API Driver: 25.20.15021.1007
Dedicated VRAM: 8068MB
Monitors: 1
Output HDR: ON
Display Width: 3840
Display Height: 1080
Render Scale: 1.00
Render Width: 3840
Render Height: 1080
Texture Detail: ULTRA
Shadows Detail: ULTRA
Draw Distance: ULTRA
Anti-aliasing: ULTRA
Anisotropic Level: 16
Tessellation: ON
Ambient Occlusion: ON
Obscurance Fields: ON
Motion Blur: ON
Vertical Sync: OFF
Reduce Mouse Lag: OFF
No way to explain the incredible framerate improvement other than CF is working....