Max power dissipation is the max amount of heat that the transistor can produce without damage.
Max current is the max amount of current without damage.
If you exceed the max power dissipation but cool the transistor better than normal (with a fan or with liquid nitogen) then it is fine.
But if you exceed the max allowed current then it will probably burnout the connecting wires inside.
A PNP transistor sources current (its collector output goes high).
An NPN transistor sinks current (its collector output goes low).
But an NPN transistor used as an emitter-follower can source current but has a Vbe voltage loss.
A PNP transistor can also be used as an emitter-follower to sink current but has a Vbe voltage loss.