Well H4 is also great for off road depending on what you are doing. L4 is more useful in technical/steep sections or where you are towing someone out. One thing, try cycling your truck into L4 occasionally to keep everything properly lubricated and working.
As for the center dif lock, DO NOT lock it when you are on paved roads, unless you are going totally straight. It, like the L4, is good to cycle on and off occasionally, but do not go around town driving with it on, it will lead to very bad news. Any time I am off road (and not on high grip surfaces like rock) I usually have mine off since it also disables the VSC and lets me slide the 4Runner around a little.
Hope this helped and enjoy your 4Runner! :bigok: