Car smoking

One way to know is give it a compression test, all cylinder should be within 10% of each other, if one or two are much lower, it's likely a blown head gasket. A leakdown test can also check how well rings and valve seats are sealing. In your case I'd suspect an issue with valves more so than head gasket. Also a stretched timing chain or worn/flat cam or collapsed lifter can throw off timing leaving valves slightly open at TDC.

Excellent point, and easy enough to check. Anytime you have escaping pressure in a crankcase it's a good idea to check the PCV system and breather.