"so if I use them only use a couple to mimic real life, okay thanks"
Sorry I did not have the time to explain myself fully. Let's make an example:
OOB 17, unit 198. This is a bunker armed with a 100mm Rapira antitank gun. Here is a picture of the gun
http://svsm.org/gallery/100mm_mt-12/P1020093
In order to put such a thing in a bunker you would have to leave a very large opening for it to enter and leave. And a very large loophole for retaining a meaningful arc of fire.
While I have seen some bunkers built exactly like that they are extremely rare for several good reasons.
Tank turret bunkers are more common, as that was a common way to dispose of older tanks. For example here in Italy many obsolete tanks (Pershing etc) were used in such a fashion to create defensive strongpoint against a Warsaw pact ofensive. The soviets recycled many of their JS tanks to create strongpoints on the Kuriles and such and so on.
One would need a detailed map of such lines to be sure but I would recon that a couple of them on the typical SPMBT map would be just right.
In general the majority of "modern" bunkers (outside the rare cold war defensive line) would be either simple shelters or machineguns positions at most, built out of precast concrete and/or sandbags and such.
As for general effectiviness the germans seemed to be fond of the their Pantherturm bunkers.