If you want to upgrade the boot drive, you can install up to a 2 TB NVMe/PCIe SSD. You also have the ability to add a 2.5" 2 TB SSD as a second drive. As for RAM you can install up to 32 GB of DDR4 2666 RAM (though Crucial lists 3200 as well but it will run at 2666). The Toshiba is a lower performance entry level drive so I would suggest something like the WD Black or a SAMSUNG 970 or AData XPG or the Crucial P5 series.

Thanks man

Glad to help out!

Just like to confirm that Samsung Evo 970 Plus will work on G3 17 3779 . I've went from reads and writes of just over 500mbps to over 3200. So if your looking to upgrade your 3779 this is a great option.

After using Samsung Magician my speed has shot through the roof . Here's my samsung's evo 970 plus speed test . And to confirm Crucial 3200 MHz ram will work but as mentioned above it runs at 2666 MHz . 
G3 17 3779

I know this is an old thread, but the spec sheet for the Dell laptop, on Dell's website, says it only accepts an m.2 nvme drive up to 512 gb capacity. You were able to put in a 1-2TB drive and it worked?