My normal light EDC is a Fenix LD01 in my pocket, backed up with a Fenix L1T and Petzl headlight in my bag (or pocket if I am anticipating needing a light and want to carry something above the LD01)
The LD01 is carried in a small wallet in my pocket that holds the rest of my EDC (so it can all be easily removed as one rather than fishing out a collection of loose items every time I change trousers) which holds everything securely in place where I want it.
I am not normally a fan of belt EDC, as I prefer having everything kept hidden, except when I am camping and the L1T and knife go on my belt for easy access.
As for the 'one is none, two is one' approach, I partly follow the rule... Normally I don't *need* a light all that regularly, so only carry the LD01 and can easily make do without if necessary, but if I anticipate needing a light beyond looking in the back of cupboards or finding loose change under the car seat then I carry the L1T so I have a bigger main light and the LD01 as a backup. so 'two is one' when needed...