Number two cylinder misfire

If the rear O2 tracks the front one voltage wise it's not a good sign, another test would be to use an IR thermometer and look at the temperature of the front of the converter versus the rear. I'd worry about the misfires first though. The converter won't cause misfires, but misfires can damage the converter. This shows a few tests:
https://www.2carpros.com/articles/how-to-test-a-catalytic-converter

So far the ignition side looks like it could be a cause of the misfire, but it also looks like the engine is running rich.
To test the MAF you can check the output voltage if your scan tool will show it or the airflow in grams. Just turn on the key, don't start the engine. The flow should be zero and the voltage should be zero as well. If either one is something else either the MAF or the ECM is faulty.

Sounds like someone has been doing some alterations. These are the ignition wiring diagrams for the 2000 and 01, the coils are different with the 98-2000 using a coil with a single power feed and 2 control wires while the 01 used two coils with two power feeds. That really shouldn't be an issue, however if that is really an 01 engine, that could cause an issue as they changed multiple items in the engine control system and the engine itself between 2000 and 2001. What makes me suspicious is the number in the last image, that looks like a salvage yard number written on there for tracking and warranty purposes. Looking at the crank sensor and cam sensors, they look the same but the part numbers are different in the books which usually means the sensor was also changed in some way. Plus internal parts for some items are different as well, the camshaft for instance shows a different part number between 2000 and 2001 but uses the same cylinder head. The MAF is a different part between them as are other important parts. They are designated as a Beta 1 engine through 2000 and the 01 is a Beta 2 engine. To confuse things even more they changed things using the build date so a car built before 3/10/1999 used one engine while ones built after that date had different parts.

However if it was running okay prior to this things may be set up correctly but it also may have been a "well it runs, ship it" situation and something wasn't quite correct and has now caused a problem. What I would do is try to determine what that engine really is then at least you know what you have. For that I would find any numbers you can on the engine and see what those turn up online. If you can contact the people you got the car from they might be able to shed some light on the issue as well.

That would be a good starting point. Hyundai used the same basic 2.0 engine in two US vehicles the Elantra and the Tiburon but with slightly different parts and programming for the cars. Then to make it more confusing they stopped using the Beta 1 in 2000 on the Elantra but used it until 2001 in the Tiburon. From what you have I suspect they got a used engine and swapped over the parts from the original to the "new" engine so the parts fit. The question then is, what was the "new" engine actually from and which version is it.
Because it did run okay I'm thinking the parts are likely correct, but it would be good to know what you have. For instance they altered things like the fuel injectors on the newer engine to flow more fuel, if you had the 2.0 from say a 2001 Elantra with the Beta 2 engine then the reason it runs rich could be in those injectors. At least knowing what it actually is would give you a start.

The numbers are wire sizes..5 is 1/2 mm. Green, white and brown would be the colors for a Beta 1 harness. That would match the coil you have.

There should be an engine number stamped on the block either below the thermostat housing or on the flange on the transmission side of the block. Google that number and it might help with the engine information. I almost think you have the newer engine but the wiring was altered to make it work and parts from the old engine were used because they were okay. Something like the old engine blew and this one was put in using the working parts from the original. In theory it should work unless there were internal changes, which there were. However it did run so the trick will be why did it suddenly stop running. Because it looks like the engine is running lean by the way those plugs are sooted up I suspect that the injectors are larger than the "old" engine, that carbon then creates a way for the spark to go and you get the random misfires. What I would probably do at this point would be to install the new coil, and new plugs, or clean the ones you have really good to remove the carbon. Then see what it does. If it runs okay, then I would consider doing a top cylinder cleaning using something like seafoam to remove some of the carbon. Then see if it still makes the plugs carbon up. If it does then I would check the fuel pressure to make sure it's in spec and maybe pull an injector to see if the part number on them matches the ones for the year and engine the car should have in it.