So, I have been using VATS less and less. But I still like to tinker with the mechanics! So I did some testing with different levels of AP Regen!
First the default AP regen rate is 6. As in 1/6 = 16.6667. There is a player attribute that controls how fast your base AP regenerates. The default is 6. Dividing 1 by the value gives the total time it takes to regen your AP. Now this is your base naked AP, if you are using drugs or equipment to boost your AP then it will take longer to regen. Just to be clear your base AP is soley from Agility - before any buffs.
But enough boring geek talk, lets compare different things that can impact your AP regen rate.
First are the perks action boy. Each level says it reduces AP regen by 25%. What it does behind the scenes is increase your base AP regen variable by 1.5. So that 6 becomes 7.5 with one rank. Or you will regenerate your base AP in about 13.3333 seconds. Taking two perks boosts your base rate to 9. So it takes 11.1111 seconds to regen your base AP. Now 11.111 is NOT 50% of 16.667! Is it worth two perks to cut 5 seconds off? Not really in my book.
So, the next thing are the items that says they increase AP Regen by a flat number. Like the Commando Combat Armor or the Power Armor Mod. The legendary combat armor will increase that base stat from 6 to 11 - a solid 5 points. More then 3 levels of Action Boy ( if you could take three levels!). With a base stat of 11 you will regen base AP in just 9 seconds. The power armor mod will boost in by 6 points - so regen all your AP in 8 seconds. Decent.
But now for the big daddy of all AP regen effects - Jet Fuel. Jet Fuel will boost that AP regen by a solid 10 points!. So that 6 becomes 16, or regen your base AP in 6 seconds. Plus it lasts for a solid 8 minutes - up to almost 30 minutes with all the Chemist perks. Pretty awesome. That is equivalent to more then 6 ranks of Action Boy!
Jet Fuel + Commando Armor gives you a massive AP regen of 21. However, it really does not impact the AP Regen THAT much - dropping it from 6 seconds to 4.5 seconds. Defintely dimishing returns here.
Not related to AP Regen, but Ice Cold Beers will regen a flat 35 AP. Like the stamina potions from Skyrim. With Party Boy 2 they regen 70 AP.
But the big take away is that Action Boy/Girl are just terrible perks!! There are far better ways to regen AP.