This post is about how I manage to successfully install RemixOS 64bit on USB 3.0 stick and boot it on UEFI. If I want to use Windows, I remove USB stick. If I want to use RemixOS, I just plug the USB stick on USB 3.0 port and turn my laptop on.
5) Look in your BIOS for "SECURE BOOT" and DISABLE IT
7) Change it to "LEGACY" and ENABLE the option "EXTERNAL DEVICE BOOT". Under BOOT PRIORITY, select "EXTERNAL DEVICE" as 1st Boot Priority (just as the picture bellow)
9) EXIT AND SAVE from BIOS settings
10) It should boot directly to USB stick. Here I had the problem that everyone had, where the USB stick could not be identified.
11) Just unplug the USB stick and plug it back to USB port. It should be recognized pretty fast and finish the installation process of RemixOS.
12) Once it has finished the installation process, RemixOS welcome screen should come up. Just follow the setup.
13) Once everything has been configured, reboot your computer and enter on BIOS. Change back from LEGACY to UEFI and you will be able to use Windows (with USB stick plugged out) OR RemixOS (with USB stick plugged in).
By the way, the RemixOS Installation Tool takes your USB Stick and partition it into 3. In my case, a 32Gb USB Stick got 10Gb External Storage, 3Gb System and 16Gb Internal storage. So do not worry about creating a bigger internal storage since the installation tool does it for you.
Hope it has helped to answer and solve a lot of problems.