Macrium Reflect

Hi,
I am using Macrium Reflect as my main backup tool on my PCs.

I have now installed it on my Laptop, and it is asking me to create "rescue media" (I created a DVD for my desktop with the earlier version (5?) (now version 6)).

1. Now I'm running Windows 10, should I create a new Rescue DVD? and if so, which PE version should I use?
Options are 3.1 (W_7); 4.0 (W_8); & 5.0 (W_8.1)

2. I have tried to create rescue media on the Laptop (which has no Optical Drive) so trying to use a USB drive.
When it eventually asks me to create the media, there are/should be 2 options: DVD & USB, I chose the PE5.0, but the USB option is greyed out and not selectable.
Any ideas why please?

3. Will rescue media created for 1 PC be OK on any other PCs?

Thanks

Macrium Reflect