guy wrote:"Nothng runs as root unless you say it can". Like, I am going to read all the "this app will pwn your soul" permissions before I decide whether to download it. At least it won't pwn my OS quite so easily if I have no root access to grant it.
you've got hold of the wrong end of the stick here. Do you have su installed? Does that mean anything can run as root? The program asks for root permissions when it runs, you can answer Yes/No/Just this time. If you don't answer, it takes it as no. Basically, you have su on the device and when a program needs root access it calls su (a nit like some desktop apps that pop up a similar requester when they need root privileges). There is no more danger of RandomApp getting root privileges on Android than there is of Synaptic running as root on a Linux desktop.
On the failure rate, of the Android devices I have bought in the last year, my failure rate has been 50%. You may not need backups, I do. I only mentioned them as the original reason I rooted my devices. You have a different reason, to be able to use USB OTG. If you don't want to root fair enough, that's your choice, but you also said you didn't want to use a paid app. That leaves you with no more choices, but that is also your choice.
I've also had my fair share of hard drive failures, some down to dirty power, one of which failed while writing a review of backup software for LXF. Thanks to all the backups, I didn't have to start again from scratch
"Insanity: doing the same thing over and over again and expecting different results." (Albert Einstein)