PC Help with Game Recording

Since updating my set up I've struggled getting nice, smooth recordings to post. 

In-game whilst I'm recording, I experience no issues at all, frame rates are good and there's no lag etc. However, when I review the recordings (especially if they're co-op, i.e. in someone elses world or with a group) the frame rates are terrible! They obviously spike, then lag back to single figures, even stop. 

I'm experiencing none of this whilst I'm actually playing the game?!? What could be causing this?

I'm playing at 1440p resolution, 144hz, high settings, recording using Filmora at same resolution and "best" default settings.

Rig being use:

Ryzen 5 2600 (OC'd to 3900mhz)

AMD MSi RX580 8Gb Armor Edition

16Gb 3200Mhz RAM (twin channel)

Game is running fron an SSD, recordings saved to a 7200RPM HDD (though I had same issues when the recordings were being saved to the games own SSD).

Any suggestions?

My initial thoughts are I need to scale my gameplay back to 1080p and 60/75hz but that would mean my 2k monitor is pretty useless...so I'm wondering if its something else or I need to upgrade my processor or graphics card maybe?? However, I admit, I didn't really have this issue when I ran my i5-6400 & GTX1060 3Gb system...which, should be, a weaker one for this! Then again, that was running at 1080p/60hz so maybe that small bump is the only reason? 

A couple of questions:

• What software are you recording with?  (oops Filmora, just saw that)
  
• What is the bias for work between the GPU/CPU for the rendering?
  
• Have you set the recording to a lower resolution/refresh?  That is display at 1440p @ 144hz record at 1080p @ 60hz.
  
• Are there any other Filmora settings that you have tried?
  
• On the hard disk, Sata 3? or? (I would suggest getting an SSD or another NVME for the capture process)
  
• The RX 580 may be a little weak for playing AND recording at 1440p (assuming 2560x1440)
  
• Have you monitored CPU/GPU utilization?  Anything over about 85% on either seems to have recording issues for me.
  

Not knowing the above, my guess it two things, the RX580 does not have enough power to both play and record at 1440p and the physical HD is not able to keep up with the capture process at 1440p.  The queue length within the capture software backs up and instead of crashing, the SW drops frames.

I get good recordings (1920x1200) with GPU at ~85% and CPU (all 12 threads) at 80%, but had to drop to medium settings.  I am looking at upping from the GTX 970 to GTX 1070ti (~$250 on ebay) and up from the R5 1600x to R7 1700 (~$50 delta).

I use OSB and record to my NVME OS disk (240GB) and just move the recordings to work on them.  My end game is 1440p gaming and doing exactly what you are trying to do.  So you can be my guinea pig 

...gene