The blocks that you can you have inside the scenes, are the blocks that you had loaded inside the preset... a scene permits you to manage which block is active on that scene, whic option between X or Y of that block and the master level of the scene, but you cannot change the parameters of a block 'cause it will be changed in each scene of that preset.
Speaking about the amp blocks, you can have 2 amp blocks in each preset. An amp block has also the X/Y feature that permits you to load 2 different amps inside the same block using only one at the time.
So inside a preset you can load 2 amp blocks with 2 amps each for a total of 4 amps (with the limitation of using max 2 amps at the same time).
In each scene you can choose which amp block is active with the X or Y option, so you can have these combinations:
Amb Block1 X ON - AmpBlock2 OFF
Amb Block1 Y ON - AmpBlock2 OFF
Amb Block1 OFF - AmpBlock2 X ON
Amb Block1 OFF - AmpBlock2 Y ON
Amb Block1 X ON - AmpBlock2 X ON
Amb Block1 Y ON - AmpBlock2 X ON
Amb Block1 Y ON - AmpBlock2 Y ON
Amb Block1 X ON - AmpBlock2 Y ON
https://wiki.fractalaudio.com/axefx2/index.php?title=Scenes