Indeed, the majority of the signatories to the open letter are already non-moderators who decided to join the strike to support the moderators and join in the action to hopefully get Stack Overflow, Inc. to listen to the community.
As of right now, around 1,200 out of the 1,346 total signatures are by regular users who are not moderators, former moderators, or former staff. (The number is not precise because the marking of former moderators and staff is a voluntary and manual process, so a few "regular" users aren't really, but the number is quite low.)
The open letter is the canonical resource, and includes a FAQ with a question about this precise topic; but in brief, you can decide to participate by signing the open letter (though this is of course not mandatory, if you wish not to do that for some reason) and abstaining from actions of content moderation on the sites you participate on.
In other words, this is a moderation strike, not a "moderator" strike. Everyone who has some sort of moderation privileges (vote up, down, close, delete, etc) can participate.
Many users have restricted their moderation activities to only the meta sites, so that we can help keep the discussions about the strike civil and focused.
As for "should" you, that's obviously totally up to you. If you support the strike, by all means, you are most welcome to join.
Asking and answering questions is not strictly speaking acts of moderation, though you might also want to consider abstaining from these activities - if you have doubts about the site's future, after all, perhaps contributing to its collection of user-generated content is also something you want to pause.