Portable HDD

Hi, everyone. I'm not sure if the title is as clear I intend for it to be, but I have an internal 2.5" HDD with Windows 10 installed on it that I use as a sort of test OS which I install programmes, updates, etc. on that I want to test out before I install them on my main SSD. My question is, if...

My portable hard drive is showing up in file explorer like it use to. It shows up in device manager and the partitioner but not in my file explorer so i can move files to it. Please save me. here is some system info motherboard: ASUS ROG Strix B-350-F Gaming

I connected my portable hard drive to USB 3.1 but windows asking me to connect with a USB 3.0, my hard drive USB 3.1 compatible, I also tried to connect to USB 3.0 but the same thing happing

I can get a 128GB SSD for around £20 and a PCI-E SSD for about £60. Is there a significant difference in OS usage speed and boot times of OS between the 2?