This morning I was starting my wife's Volvo (1996 NA 850 with +200k) and it had a hard time starting, when it did it almost immediately died and a buff of thick smoke came out the tail pipe.

It won't start at all. It cranks over, but nothing. It was seemingly running fine until today. The car has fresh plugs, wires, dizzy cap/rotor, coil.

Sound like a fuel pump?

 

It sounds like you need to find out if it has spark and fuel. Pull the cap and see if the rotor is turning (checks the timing belt) and let us know what you find. If you've been cranking it for a while you might want to pull a plug or two and see if they are wet or drenched with fuel.

Fuel pump or relay may have shut down or failed or might be a temp sensor too. Need to start with the basics and can go from there.

 

Yea, check for codes, and with these old cars, check compression if you have the other 3 items. Fuel, spark, air... compression.

 

What color smoke?