I haven't used mine at an open mic... well, I've never done an open mic.
I'm plugging into my own equipment. I did find the X20 with the LR Baggs Element Active pickup is a bit hotter and heavier on the bass than the pickups in my other guitars. No big deal to EQ it, but I would assume at an open mic, someone is taking care of the sound.
The single tone control on the guitar wasn't enough on mine. I am running into a TC Helicon Play Acoustic. With my other guitars, I have the BodyRez balanced at around half; less with the X20. I take the bass down a bit on the amp. That is run with a direct line to a Bose L1c.
I have been using this rig (with a TC Helicon Gxt prior to the Play Acoustic) for years. There is a bit of adjustment with any of the guitars I use, but I have been able to do that at the guitar (Taylors with ESv1.2 and ES2, B-Band on the X7, Fishman Prefix-T on the Shorty). With an unbalanced guitar cord, the ES2 is hotter and bassier than the ES1.3 on the Taylors, so it isn't unusual for the difference.
Of all of these, my favorite is the B-Band; it seems to give me the most control right at the guitar... but, those controls are tiny. Set it once, then I don't mess with it. Some don't like the esthetics of the barndoor pickups - I see it as a tool, and it doesn't bother me.
So, maybe more info than you wanted, but just showing that every guitar is different. I see no issue with the X20 at an open mic.