The level of enemies and loot in dungeons is determined by a couple of factors:
- Your level when you first enter the dungeon (that is, change zones into it)
- If the dungeon has a minimum or maximum level
The UESP notes this (and here) as does another question on the site.
Some locations don't have their own "zones" - like ruins and so forth. It's not altogether clear to me what locks you into enemy and loot levels in this case, since you can be fairly far away and still encounter enemies.
I don't believe the act of discovering (but not entering) a location that is completely interior locks the level of the stuff in it, from personal experience.
The UESP also notes that there are level ranges for certain dungeons, and the further off the beaten path something is, the higher the level range is likely to be (if there is one).
My suggestion to you would be to explore as you see fit. There are a lot of places to explore, and unless you grind around visiting every location on the map while not leveling yourself up, chances are pretty good that you're going to have plenty to do from level 1 until whatever level you reach when you stop playing.