Hello @decky
Yes to both.
The Thimphu motherboards have also had the GTX 1060 installed on them in certain models.
2 things you need to check first...
1. Your Radeon 380 is using one or two 6-pin power connectors I assume?
The Nvidia 1060 might need an 8-pin power connector. You need to verify that your power supply will have that connector in your model if so. HP Specs don't give me that specific of details to know what yours has. If it does not have one, you will need to replace the psu with one that does. 500w minimum.
2. Double check the inside of the area for whatever 1060 card you are going to order, to make sure the dimensions will allow it to fit. It should fit whatever one you get since is had a 390, but its just a good idea to always check first.
Uninstall the AMD video driver before installing the Nvidia card.
You can absolutely install a 2.5 inch Samsung EVO 850 if you are replacing the HDD, this would be easiest.
You will probably also need a bracket mount to convert from the 3.5 HDD to the SSD bay.
The Thimphu Motherboard also has an M.2 m-keyed NVMe SSD slot that's located next to the PCIe slot the video card installs in. Users have mentioned here on the forum that it works for a bootable drive.
You need to have the current bios update installed and would have to purchase an extra screw for the m.2 drive (there is no screw provided on the board).
The HP Recovery Media might not install to the SSD as it looks for the same size or larger hard drive that originally came with the PC. If not, you would have to install via the Microsoft Media Creation Tool or use an image of the HDD to place on the new drive.