Do you have any particular questions on compatibility? Currently, this is quite vague.
1.0 figures simply follow the rules outlined in the 2.0 rulebook. An example is having access to relevant speed/attack type proficiencies (double time, surge, gang up)
Special abilities not listed in the 2.0 SAC were simply not included on any 2.0 releases, however, that does not retroactively remove 1.0 special abilities.
Some 2.0 models are quite powerful (Scalesworn Honorguard, Geddion Longblade, Chroma, Vharigar, and maybe Tazia) and styrene interactions add another level (Swarm of the Damned, Death Throes and Explode Undead, Ward of Light denial, Book of Lightning spam, Deathseekers and Call Familiar [which is it's own can of worms], buff and even simple stat stacking, especially with Psychic reflection), however, many 1.0 Mage Spawn and 1.0 mounted figures become similarly efficient with access to 2.0 proficiencies. Weres, Wraith, War Kruggs, Light Lancers, Fell Reapers and the Mounted Dwarves immediately come to mind.
This consolidated and annotated rules document may help.
The Mage Knight Resurection
FAQ states warriors are allowed to use Items, Relics, and Spellbooks if they don’t have slots in their bases. When a Mage Knight warrior doesn’t have item slots in its base, it is considered to have three item slots; place items on its HeroClix character card to represent items carried by the warrior. I personally disagree with this "careless" adjustment as slots affected a units point cost.
Hope some of the above answered potential questions.