IX35 misfire ?

Morning all.
My wife called me at 3am saying her car was driving so badly and the check engine light was on while she was on her way to work today at the airport that she pulled over and called me. As this car burns oil and the oil sensor/light doesn't seem to work the first thing I did was to add 2L as I couldn't see any on the dipstick (the engine was still hot), Then I started it-engine light goes out but it felt like it was on 3 cylinders, idle-3000rpm felt the same, Apparently this is what it felt like before she stopped.

She complained of a shudder when it got a WOF and the mechanic changed the plugs about 10-20,000km ago and all was good.

So my questions are;
Could this be a coil pack ?
Buy 1 new coil and replacing each one until the misfire stops ? or just do all 4 ?
Is it worth buying an OBD2 tester to check the codes first ?

The car's is a 2014 IX35 2.0 petrol 210,000km Front wheel drive.
I'm mechanically minded, but cars have never been a strong suit for me.
It's parked on the roadside about 2m away from the fog line so I'm ok with doing a quick job on it there and then, the follow up question is; if the oil level was ok and I've now over filled it is that an issue ? I'm too old/round to fit under on the roadside to drain some. It's a 20km motorway trip so I'd have to call a tow truck.
Alan

I rarely give advice on cars but this is what Id do. If it has separate coil packs see if you can get to the plugs and with the car running unplug one at a time and plug it back in, the cyl that's missing will make no difference when you unplug it. Once you find which one it is swap it around with another one and see if its the same one. If not and its still the same cyl missing pull the plug out and have a look at it for a start. pm me if you want

obd2 tester is worth the investment. hell even my 30 dollar one from TM solved a really intermittent fault

Check what plugs it's meant to have and see what ones are installed. You would be surprised how many times people install the wrong plugs.

definitely run a diagnostic on it so buy or borrow one otherwise you will chase your tail and a multitester to check the resistence on the plugs occasionally one will fail or if it uses oil then one could be completely rustproofed(oiled up) to the point of not sparking