Disconnected my battery last night for about 20 minutes while I was exploring the inside of my dash. Since then my 4runner is idling at about 400 RPM rather than the usual 500-600. Also seems to respond slower and be more jerky when hitting the gas from a stopped position.

Driving it otherwise feels normal above about 10 mph.

I've put on 30k miles since I got it 2 years ago, right now I'm sitting at 136k miles. I have no idea when the spark plugs were changed before that but I just read on another thread here that spark plugs should be done every 30k so I'm preparing to do those also.

Also today I will probably disconnect the battery again and leave it disconnected for an hour then reconnect it.

There's no stalling and no starting up problems either.

Can anything else cause this problem?

2005 4runner SR5

You reset the ECU when you unplugged the battery. The computer is having to relearn all the short term and long term fuel trims again. This is perfectly normal. I don't know how long you've let the engine run since this, but it usually clears up after letting it idle for about 20 minutes or driving it for a while.
If it persists after a few days, then you should start looking at other things, but odds are, if it ran/idled fine before the battery disconnect it'll fix itself.

I've only let it idle for about 30 seconds each time before driving, but I've already driven about an hour on it total but at higher speeds.

I'll keep that in mind though and if it doesn't go away in a few days I'll probably come back.

Everyone uses the battery disconnect rationale way too freely. There is a finite amount of code and subsequent operating parameters for these engines. My car resets itself immediately after firing when the battery is reconnected. 10 seconds of idle is all it takes. Never longer. Ever.

Should I unplug the battery again and have it re-try to get the idle right?

I wouldn't disconnect the battery again. Let the ECU do it's job and figure things out. If you disconnect the battery, it has to start back from zero.
Just let it idle for 10 minutes and see what happens. Start it, leave it in park, take some selfies, check Facebook, send dirty texts to your girlfriend...boom, there's 10 minutes. Easy, huh?
07V8 has had a different experience, but keep in mind all vehicles are a little different. Your ECU may be having to adjust for a small rich or lean condition which may take more time.
Maybe you do need new plugs. Maybe you do have a small vacuum leak somewhere. Maybe you do have a leaky injector. But, maybe you also just need to let it idle for a little while. Do the easy stuff first.

Just my 2 cents.