I've been using a very old system for years with vMix HD. An AMD Ryzen 5 and 1050 TI. with 16 gb of memory. Recordings and streaming were great. However I wanted to be able to add the multicord feature so I could ISO all of my inputs. this last month I finally built a new computer and upgraded to the 4k edition of vMix. I based the build off of the Ruby system. I've played around with many output setting AVI with compression and without. MP4 at 20 mpbs and 8mbps audio at 128 and. I capture all 3 cameras and the main output. The main output is perfect. But the iso inputs are terrible and the audio is useless. I can max settings and still only ever use 15% of my GPU memory so that isn't the issue. I've played around with the input settings lowering the audio quality coming in to the software. I'm not sure what to do now.

Inputs are 3 over HDMI cameras. and a Zoom Live Track 8 with IO setting bring in 4 channels of audio.
Main Camera Sony A6300 > direct wired to capture card (most drops) 60fps 50mbps
Second camera > Sony A6400 using ACCSOON CineView HE Wireless 60fps 25mbps
Third camera > Sony A6400 using ACCSOON CineView HE Wireless 60fps 25bps

Vmix Setting 1080 60fps
Record settings vary, trying to get rid of dropouts.

for reference the Ruby setup is
Motherboard MSI MPG Z690 Carbon Wi-Fi DDR5 Motherboard
Graphics Card NVIDIA GeForce RTX 3060 Ti
Case ATX Case (Corsair Carbide 275R Tempered Glass Case in photo)
SSD Samsung 970 EVO Plus NVMe M.2 1TB SSD
PSU 750W ATX PSU
Capture Card AJA Corvid 88 or Blackmagic Decklink Quad 2
CPU Intel Core i7 12700KF
+ Cooler Master Masterliquid ML240L V2 ARGB AIO CPU Cooler
RAM 16GB (2x8GB) DDR5
Operating System Windows 10

My setup is
Motherboard MSI B760 Gaming PluIs WiFi Gaming ATX Motherboard
Graphics Card NVIDIA GeForce RTX 3070
Case Antec Ax Series AX61 Elite ATX
SSD 2TB WD Blue SN580 NVMe SSD
PSU Thermaltake Smart BX1 750W 80 Plus Bronze Power Supply
Capture Card ACASIS PCIE Capture Card HDMI 1.4 1080P60HZ PCIE 2.0 X4 20Gbps for Video Capture
CPU Intel 15-13600k Processor + -ID-Cooling SE- 225-XT 5 Heat pipes CPU Air cooler
RAM Patriot Viper Venom DDR5 32GB (2 x 16GB) 6600MHz
Operating System Windows 11