I keep seeing these persistent myths floating around as people try to fit their ships. Just for the record, let me try to debunk some of them.
Of course, your mileage may vary. Most folks will probably disagree with something here. I'll make my case as clearly as I can, and am always happy to be proven wrong.
Also, many folks may deny that these myths are even prevalent. All I can say is that they didn't come out of nowhere: I've helped a lot of people fit ships in a variety of situations.
Myth: "Racial" ECM jammers that target a particular race's sensors are much stronger against those sensors than "Multispectral" jammers which target all sensors equally (albeit weaker against other sensors). Thus, if you have four jammers, you should should fit a "rainbow" of one of each racial type. This is just common sense.
Reality: Common sense and probability are not close cousins. If you do the math it turns out that:
Four multispectral jammers are always going to be better against a single target than one matched racial jammer and three mismatched ones.
If you split the four jammers between two targets of with different sensors, each matched-mismatched pair will be about the same as two multispectrals.
Multispectrals are also just easier to use. No using the wrong jammer in the heat of battle, because there is no wrong jammer.
Unless you have a pretty good idea what sensors you are going to be going up against, just fit multispectrals. This is likely by design: CCP provides racial jammers for fleet setpiece battles, and multispectrals for general use.
My ecmulator tool will help you calculate the jam probabilities for your fit. Play with it to get a feel for all these things work.
Inertial Stabilizer Signature Bloom
Myth: You should avoid using Inertial Stabilizers because they make your signature radius bigger. Use Nanofiber Internal Structure instead.
Reality: The signature bloom of an Istab II is 11%. This is rarely ever going to make a difference to anything. In return, you get a 20% inertia modifier, which is a big deal. If 11% is too much for you, you can use a Type-D Restrained Istab, which cuts the sig bloom to 8% and gives an 18.5% inertia modifier.
Meanwhile, a Nanofiber II gives you a 20% penalty to hull strength and a 15.8% inertia modifier. In return you get a 9.5% velocity bonus you may or may not have needed. The restrained version gives you 14.5% inertia bonus and 10% structure penalty.
Fitting Nanofiber is like dual-tanking. There may be situations where it is what you want, but you've normally gotten away from the goal of the fit. You usually fit an inertia mod to get your align time down. Do that as best you can and get away. Then you don't have to worry about the sig radius.
(Stacking penalties make this worse. If you have to fit an extra Nanofiber to get your align time to where you want it, it's kind of game over.)
T2 Fittings Best Fittings
Myth: Tech 2 fittings are the Holy Grail of standard fittings. Accept no substitutes if at all possible.
Fact: The situation is pretty complicated, and is really per fitting.
For some things, the Meta versions are just flat-out better than their T2 counterparts. They are almost always substantially cheaper, and may have nice niche capabilities that you want. They are often easier on fitting resources.
It always pays to look in detail at the variants of the module you are about to fit and choose the best one. It may surprise you which one that is.
Bling Fittings Best Fittings
Myth: You should always fit the best fitting you can afford to lose. If that's a high-end officer mod, so be it.
Reality: I mean, who doesn't want better? The faction, Deadspace and officer mods are almost always a little better than their cheaper counterparts.
However, we are often talking about crazy amounts of ISK for an extremely modest improvement. At some point, if you are going to spend that kind of space money…
Find a better ship. The bonuses you can get by picking a fancy hull are just way better than anything fancy mods are likely to do for you. My general rule of thumb is that when the cost of fittings exceeds twice the cost of the hull I start looking hard for a ship upgrade. I can usually find something appropriate.
Besides, it seems to me that can afford to lose a 1B ISK fitting is different from don't care about losing a 1B ISK fitting. Anybody in the latter case should ignore this section and just put all the bling on all the things. Lucky you.
Active Fits Best Fits
Myth: An active-rep fit (I lump in passive shield tanking here) is always the goal, because an active tank can take more damage. Buffer is only for fleet battles where logi ships do the active repairing.
Reality: It is easy to calculate when active tank is better than buffer tank. Take the amount of EHP/s your active tank yields and multiply it by the largest likely duration of your fight. You now have the amount of buffer EHP you would need for an equivalent tank. You will sometimes be surprised by finding that this much buffer is easy to add.
Oh, and if you don't have enough buffer to survive an incoming volley, the hypothetical future value of your active tank is exactly zero. You may need to add some buffer anyhow, at which point you're effectively sort-of kind-of dual-tanking: using up buffer and active slots rather than concentrating on the "better" of the two.
The point is that there's no hard rule. Active tank is generally better when you expect to engage in extended combat and have a ship sturdy enough to take damage bursts. Buffer tank is generally better when you expect to be away or dead quickly and prefer the first option. There are exceptions both ways, and sometimes a combination works best.
Fitting Ships Is Hard
Myth: Fitting ships is hard.
Reality: Fitting ships is hard.
OK, this isn't a myth so much.
The biggest limit on ship-fitting ability is time. It takes time to learn the stuff you need to, and time poking at many, many fit variants to get a good one in a particular case.
I haven't the slightest clue about fitting capital or supercapital ships. It would probably take me hundreds of hours to learn, and it just doesn't come up that often for me.
Also, I have no experience flying capital ships, or even watching other people fly them. Thus I don't even have a good idea of what scenarios will come up. Scenarios are really important in ship fitting. You fit for a target set of things you expect or want to happen.
If you have access to a fitting expert, use them. There are a lot of players out there that fit better than I do. Use an expert to get a good fit, but also to learn how they think. A lot of what little I know is gained by that second thing.
Hopefully some of this is helpful. If you want to discuss, feel free to contact me in-game.