.2-.3 belt

and bulge til you lose 1knt, reduce your bulge to get that knt back

0.2 or 0.5 belt and bulge till you go 40 knts assuming you have a proper crew (4 engies ETC) or cut on the bulge and try going 42 (for ise and Nagato since Yamato with a standard setup won't go faster than 40 no matter the armor).

Same for the Kongo?

Or do you go without Armour?
Which Engine to use for the Kongo?

So you'd basically advise to use maximum range/speed, right?

So the Type 98 L 12.2 guns and light ammo?
AP for backup ammo?

IJN Armor is generally crap ano no ships i know of can effectively AW at all.
Therefore the 0.2 belt + bulge till you loose speed is pretty much a rule to follow with all ships from DD to BB6 (CVs can pack as much bulge they want since being fast is not as important to them).
Kongo with at level crew should go 42-44 knt when using flanking speed (OH).

The best Kongo guns are 14"N since they have far better firepower than 12.2"L slightely more range and better spread.
They require higher level gunners but you should switch to them when you can.

Use a Heavy BB1 engine.

Basically all IJN BB setups (and other nations for the most part as well) can be defined by several rules:

Go about 40-42 knts (with the exeptions for some EBBs that can go stupidly fast with EBB guns).
Have no deck.
Use 0.2" belt.
Has at least some bulge (depends on crew level since higher level crews are heavier and force you to reducing bulge to maintain speed). 
Uses heavy engine. 

There is also a SW (Speed whore) setup possible for some ships but i have no experience ot this topic bar the fact it's mostly used by RN BBs. 

You should read the stickies...

I've actually tried this. If you pot as much deck armor as possible with around 500 or more SD you can actually survive a full salvo from a Montana and still have half of your DP left but it costs a lot and make sure you have at least lvl 75+ engies but it actually helped me a lot and you will be suprised how long you survive and what you can survive with that crap armor

I configured my Kongo according to your rules and my top speed is only 20/34...
I got the following setup:

BB1 Heavy Engine
3 Engineers 49,49,43
2 Repairers 43,42

Used the 12,2 guns with 2 normal and 1 ap each.

Then some AA DP guns 2*5" with just 1 AA ammo..

Are my Engineers too low?
0.2 belt and as much Buldge as I could fit without losing further speed (28)

Could throw the AA away, as it's not much use anyway...

Engineers only increase OH speed. Never cruise speed.
As a matter fact Kongo should be able to speedcap without engineers at all.

Anyway... wrong engine. Look for a engine with the most Horsepower.