Read up some more my friend. The Romans used a variety of ways to crucify people. The x-cross being among the other two you already listed.
It is also widely known by now that the depictions of Jesus being nailed through the palms and feet, are almost certainly wrong. More likely would be the wrists and the heel bones. Which just by imagination, would have Jesus in a much different position then he is usually depicted.
There was a show on Jesus being crucified.
You have to think about efficiency. The Romans were about efficiency. The "T" shapes are more effiecent shapes to be carried either by the condemned or the soldiers.
An X crucification would likely mean two heavy cross beams of the same length---weighing well over 200 pounds. That is not efficient to carry for two Roman soldiers and the. To have to set it up.
Also, the Egyptians used to crucify people upside down.
Being nailed by the hands...nobody mentioned that except for you.
It doesn't make sense to be nailed by the hands---the hands contain webbing and would tear, because the hands cannot support the weight. So, you put a Roman nail through the wrists---more support. And also, if they choose, to do through the hands, for either added measure, or added torture.
Also, throught the ankles. The point is to have the body hang as form of torture.