nope! i mean T4, there are a lot more sizes than you mentioned including a tiny T2 my friend.
peat pellets work the best for me, they are good for growing, thats what they are for. i cant stand rockwool. its hard to judge dampness. just when you got the right amount of air in there they dry up and wilt the dam clones. if you like rockwool fair enough but if you havnt used it before i suggest staying away from it. a soiless mix?? what do you think peat is?