Anyone compared the green to an ischell?
Not me.
But the Ischell is a contact mic, which means that it reacts on vibration of the mic body, whereas the Remic is an air mic that reacts on vibration of air pressure.
Air mics are rather sensitive to higher frequencies and pic up everything that reaches it via air. That means a lot of cymbals in it when you are not too far away from a drummer.
Contact mics are mostly sensitive to the body they are attached to. So it depends where your top is directed at (and you might be able to influence it by turning the bass). Also bleed from other sources that is transferred via air sounds rather dark, since a lot of higher frequency content is reflected by the top.
I use a mic for mostly acoustic groups, where only a few instruments are amplified for FOH.
If it might get a bit louder (drummer, bigger groups with a lot of wind/brass) it might make sense to send mic and contact mic/pickup to FOH and only use the contact mic/pickup for your amp.
I did use an Oktava MK-012 (SDC) through the underlength, an Audio-Technika ATM-35 (Electret), an Ehrlund EAP (piezo foil contact mic) and a AKG C411 (electret contact mic).
I also used bridge wing, bridge foot and adjuster pickups, but that’s not the point here.
The AKG C411 works similarly to the Ischell. I like it a bit better than the Ehrlund for sound (more highs), but if it gets louder it might feedback earlier than the Ehrlund and/or at a higher frequency.
Nothing beats a good air mic for sound (except a better one), but the problems of sound separation and feedback often don’t make them an option. There should at least be a fallback option immediately available if an air mic is used live.