A few observations after using the H2 Essential for a little bit:
Out of the box, the recorder picks up from it's front microphones, meaning if you are holding it directly in front of your face, it will pick things up in front of you really well, but you will be directly behind it, so you will sound odd. No biggie, just switch to recording from the rear inputs instead, unless you are not the subject of your own recording, then probably use the front inputs.
The front/rear microphones are always recorded as separate tracks. There is a mix file, but, HURRAY! Unlike the H4E and H6E, you can turn the mix on and off if you don't need or want it. I hope they bring that to their other multi-input recorders. I never use the mix on my H6E, as I prefer to load each track into my DAW for further processing if recording more than just a single mono or a stereo pair.
You can record from the 3.5mm input and the front microphones at the same time. These will be recorded to separate tracks and/or the mix file, depending on how you set that up. When something is plugged into the 3.5mm input, it is always assumed active. Pressing the button to toggle what would be the rear mics on and off does nothing, and produces an error beep. When the 3.5mm input is unplugged, the rear microphone, if it was already on before, is not re-enabled, so you'll have to turn it back on if you want to use it.
You can record in either stereo or raw M/S mode. Raw M/S gives you the ability to adjust the stereo width in post production with an M/S decoder, and allows for some further flexibility. In such a configuration, what would be the center of your sound stage is actually on channel 1, which would be the lefdt channel on a normal stereo recording, and the sides are on channel 2, or the right channel. What makes a realistic stereo image from this happen is basically making a copy of side, panning the original to the left, flipping one of those copies out of phase panned right, then mixing it back in with the mid. Or, you can reverse the panning or phasing of the side to flip the entire image around. Changing the side gain is what determines how wide the stereo image is.
If that all sounds really complicated, don't worry, the recorder's encoder does all that for you, and there are a ton of ways to do M/S decoding in a DAW or two track editor if you want to mess with a raw M/S recording. If you don't care about any of that, then just record in stereo, adjust your pickup pattern between 90 or 120 degrees, and you'll get something reasonable anyway.
When M/S raw is active, what you hear in your headphones as the device records is the same as what you would hear with the device set to 120 degrees. If you were, however, to play that raw M/S file back without the appropriate decoder, it would sound very odd.
As is typical with mid-side matrix configurations, I'm not really a fan of what they call 120 degrees pickup, which is essentially just mid and side at the same level going through an encoder. Yes, it has a wider stereo image than 90 degrees, but phasing is more obvious on the extreme left and right. I would probably decode a raw file with the side gain somewhere between where they have it for 90 degrees, and where it is even for both mid and side, which is what generates the image at 120. I'll experiment with that more later.
Plugin power on the 3.5mm input can be toggled on and off, unlike the H1 Essential. This is great if you use lavs with a battery box, a line level signal, or another microphone that provides it's own power, where you don't want DC power going to whatever is on the other side of the 3.5mm input. The H4 Essential also allows for this, as does the external module for the H6 Essential that adds two XLR inputs and a 3.5mm stereo jack, because the H6 Essential doesn't have a 3.5mm input by default.
I'm pretty sure the threshold is the same as the H1 Essential, as far as what it can handle before clipping occurs, but I haven't tested this thoroughly yet. As with all the other Essential recorders, there is no actual gain staging, however, you can adjust the output of the microphones and/or the mic/line input that gets sent to the file in the mixer, which operates pretty much like the mixxer on the H4E and H6E. This will do nothing about overloading at the hardware level, though. If something clips, you can turn the clipping up and down, but that's about it. The mixer is mostly useful when you are using multiple inputs at the same time, and you want to use the stereo mix file generated from the recorder.
Handling noise still exists, but is a bit better than that of the H1 Essential. Using a windscreen would be a good idea, but it's way more usable without one than the other Zoom recorders.
I have yet to read the manual, but I assume if you want to record something in "surround sound" and have it play back at least somewhat accurately, you would record from both front and rear at the same time, then build a track template in a daw that outputs front l/r to channels 1/2, and rear l/r to 3/4, then set your receiver up to output a composite mix of all that with a low pass filter to the sub. Save as a four channel file, or a two channel stereo mix with front and rear out-of-phase? Dunno. More on that later as well, at least to a limited extent. I have nothing on which to output 5.1 audio.