Godzilla 1978 was talking about unbalanced electrical systems where one battery is a load on the other battery (engine off) which is what you are buying into my mixing batteries of different design, size and type (you explained fairly well in your post). I would also mention circulating current since their performance curves will be different (this is more of an AC discussion)

AGM is probably the best choice for an overall performer (lots of CCA and lots of AH)especially inside the vehicle (off gas and spillage).

But with your beefy alternator you don't need a second battery ... unless you really pound/ complete ... or pound with the engine off.

I don't understand why you are so enamored with these tiny batteries, and then it struck me, you are probably out of room. All I can say on that is measure the hole you can fit the battery in and look at a manufacturer like odyssey who makes a gazillion different sizes. I would prefer a second big battery matching the one under the hood to the 12 Farad cap but that is your call.

There is always the option of squeezing a bigger battery into the engine compartment instead

 

Cause they are cheap lol

 

I can sell an awfull lot of dog poop from my two dogs preety cheep too, but it is still crap

 

Indeed!!!!!!!!! You said it. But that's the nature of some people.

 

but my cat poop is smaller chunks so it can be used a wider variety of size constrictions, it is lighter and it does not smell fowl like your dog poop. it also comes with a Kitty litter additive to increase fresh sent and improve moister absorption. Did i mention 2 bags for the price of 1 for today only!!!!!

 

Well you pretty much summed up my desire for a smaller battery.
Cheaper, and the fact that I don't need a second full size battery and wouldn't really have nowhere to put it if I did.

My capacitor didn't help with the dimming lights as much as I had hoped, but I can't say I'm surprised, and will keep it in the car for the AC filtering effect and lowering peak draws slightly off the alternator, and whatever else it's supposed to do that's not widely known.

I'm hoping an AGM battery will fill the gap between the load reaction times, of the alternator, capacitor, and battery.

 

Kinetik, Batcap, Powermaster all have smaller sized batteries.
They're not cheap, BUT will be more likely exactly what you're looking for.
Look into them.

Kinetik has a battery calculator on their website that you can use to figure out what you need for your system.
Turns out I need a HC1400 up front and 4 HC2000 out back near the amps.
Well at least for what I have planned.

 

But my cat poop is in smaller chunks, so it can be used in a wider variety of size configurations. It is lighter, and it does not smell foul like your dog poop. It also comes with a kitty litter additive to increase fresh scent and improve moisture absorption. Did I mention 2 bags for the price of 1? Today only!!!

My eyes are bleeding.

 

12 Volt 35 ah 800 Watt UB12350 Power Cell Maintenance-Free Sealed AGM Car Audio Battery by Universal Power Group is great for powering large amplifiers, high end systems and more.