Inspiron 3668, upgrades to record gaming

We have the setup described below which I have used for office work and its worked perfectly.  I have now passed this to my son to do schoolwork on and play games on.

The good news is, he can play Minecraft, Fortnite and Halo (on Steam) great.

But, he wants to try recording his games to post to share on social. 

He’s tried several screen recording tools and gets the same problem whenever he tries it, the games become jerky and don’t always respond to inputs.  They still run, but the experience jumps about.

The Machine is…

Dell Inspiron 3668 (Desktop)
Processor: Intel Core (TM) i7-7700 CPU 3.60Ghz, 36—Mhz, 4 Core(s), 8 Logical Processor(s)
Installed Physical Memory (RAM) 16.0GB
Total Physical Memory 15.9GB
Available Physical Memory 7.02GB
Total Virtual Memory 20.9GB
Available Virtual Memory 9.59GB
Page File Space 5.00GB

We have two monitors, an old VGA which plugs straight into the machine, and a NVIDIA GeForce GTX 750 Ti, which runs a second monitor.  Its not a fancy monitor.  The video details being

Primary Video Card: Intel HD Graphics 630

Adapter type: Intel HD Graphics Family, Intel Corporation compatible

Adapter RAM 1.00 GB

Secondary Video Card: NVIDIA GeForce GTX 750 Ti

Adapter Type: GeForce GTX 750 Ti NVIDIA compatible

Adapter RAM 2,147,483,648 bytes

We tried the benchmark tool UserBenchmark (results attached) and it suggest the graphics cards are limited.  This may be the case, but until its recording, the games run great, so I do wonder if there is a hard disk lag, or if a graphics are a bottleneck.  Or even if stepping up to 32gb memory would help.

I'd appreciate if anyone has any ideas what the component might be that’s causing this and how I can address it.  Im happy to go with a new GPU/more memory and a faster SSD drive, but I if there are any ideas what might be best first thing to try I would prefer not to upgrade all three, if one upgrade would fix it?

It also says the NVIDIA video card is running very poor and “Way below expectations”.  Would that mean that the video adapter is just too old/underrated, or since it says it is below expectations could that mean there is something I could do to get it used more effectively?

Any idea greatly appreciated.