Both can be detected as such.
Simply use Disk or Gparted to format the disk in desired file system. If you have no plan to use it with Windows, ext4 is better for Linux.
With this Nitro 5 laptop I have to disable secure boot first, otherwise neither drive is detected as a boot option.
Since I have never enabled secure boot in any of my laptops and desktops, I cannot say anything about your observation. I hope someone with a knowledge of secure boot can pitch in here.
Secure Boot comes pre-enabled and it's damned annoying
to say the least...
Welcome to the club 
It is the consensus on this forum - at least among the moderators.
Amazing topic. Crucial,WD HDD,puppy Linux.
As my new flash drives are to arrive (8 of them) soon do you recommend formatting them for ext4 also or does it matter ????
Thanks
Fat 32 is the format to use for the installer USB.
ext4 is for the HDD/SSD where OS is installed.
Thank you .... I'll format them with Fat 32 .... not sure what they will come with ...
Always FAT32
I see your avatar is metamorphosing everyday like a real frog.

I just wanted to add that sometime the manufacturers give you a free software (Windows only, of course) or user manual on the USB key.
It is better to reformat USB key before use even it is already in FAT32.
I also recommend you to run F3 app to confirm the real capacity of the keys, especially if they are large capacity ones.
Thanks again .... I was wondering about the software the manufactures but on these drives if they are necessary or not ... I used to copy the files to another location and then add them back when I was finished formatting ... LOL
I love your frog photo in your post hope you don't mind if I capture him and put him to good use ?????
It is not a photo.
Type ": frog :" (remove quotation marks and spaces) and see what you will get.

: frog :
You need to remove space before and after frog
Hummmm I tried but it said message to short .... anyway I love that avatar ... it looks like it was trying to open some emojis
It is indeed an emoji(originally a Japanese word 絵文字)

Sometimes people paste this error message to make their very short comment to pass this filter.
I see ... so you are multilingual as well as a talented Linux user .... do you live in Japan ???

message too short