2007 with 300k+ miles engine making rattling noises and white smoke

You have to remember this car has 300k miles, the engine is probably worn and burning lots of oil. The rattling is probably normal at this point.

The codes doesn't explain the rattling, more of emissions related codes

 

White smoke is typically coolant being vaporized in the combustion chamber(s), usually due to a head gasket fail.

If it’s coolant, the coolant level will eventually go down but it can be temporarily masked by combustion gasses backing up into the coolant, creating air in the cooling system. But overheating is a likely resultas is lower coolant levels if it is a head gasket.

You can get a combustion gas test for the coolant.

 

A/F sensors don't last forever, how many miles are on the current sensor?

Here is the step by step workup for DTC P0172 : https://share.qclt.com/%E4%B8%B0%E7%94%B0%E6%99%AE%E7%91%9E%E6%96%AF%E5%8E%9F%E5%8E%82%E8%8B%B1%E6%96%87%E6%89%8B%E5%86%8CPDF%E6%A0%BC%E5%BC%8F/Prius%20Service%20Manuals%202004/%E4%BF%AE%E7%90%86%E6%89%8B%E5%86%8C/04pruisr/05/2054m/cip0171.pdf

 

Where are you I've got a couple engines laying around out of running cars that were doing just fine other than electrical problems coils and everything were good they were running and when the engines were lifted out of the car transmissions were good too You should be able to buy these in your area from somebody with a car in their driveway to a very small junk operation anywhere from $150 to say 700 depending upon mileage condition cleanliness believability you know all the stuff.