Can I make a USB hard drive bootable with same procedure to make USB stick bootable?
 

Can I make a USB hard drive bootable using the same procedure to make a USB stick bootable?

Is there a difference internally between these two types of devices?

depends on the hard drive, I got a few HD externals my passports that are manipulated by hw/sw that prevent me from doing such a thing. In other words yes it can be done, but research should be conducted to try and find out what ones do and do not allow such things to take place. you could get ahold of an internal and use it for an external via usb adapter and cable to do this. this will increese your options in what format of media used, ie m.2, mSata, pcie, 2.5 ssd, 3.5 ssd etc.

you do know and understand the term, bottle necking, correct?

one example:

Bottlenecks and founder effects - Understanding Evolution

I do not endorse this theoretical idea.