States' rights?

Leaving the decision up to states doesn't seem all that reasonable. Either it's best to allow something, and it should be allowed nation-wide, or it's best to ban it, and it should be banned nation-wide.

Very few people would be fully consistent with the idea of letting states decide laws, i.e. letting states decide whether murder is legal, whether slavery is legal, who should be allowed to vote, etc. It seems it's mostly people who are anti-abortion who are saying states should be allowed to decide on this issue, because it's a step towards abortion being banned (which is what they want). If ever there's a nation-wide abortion ban, I'd be surprised if many of them kick up a fuss by sticking to their current position and insisting that states should be allowed to decide this (whereas I'd be consistent in my position that abortion bans are immoral).

In any case, you asked about pluralism: I don't think states' rights work well with that. While some states are quite liberal and others are quite conservative, it's still the case that within a state, there is a wide range of different interests, beliefs, and lifestyles. So by letting states decide things, you aren't allowing for the peaceful coexistence of different interests, beliefs, and lifestyles as much as you're potentially allowing states to prevent such peaceful coexistence.

Is it better to always have the option to move states than to be potentially trapped by national policies?

It's a rather privileged position to have the option to move states. Not everyone has the financial freedom to do so, and even if they do, moving across the country tends to be quite disruptive to one's life, and it may involve moving away from one's friends and family.

As for the risk of potentially having a bad national policy: I'd rather argue for policies on a national scale to try to make those good policies. I wouldn't want people in other states to suffer for the sake of some risk mitigation for myself and others.

If you're going to be consistent in advocating for smaller jurisdictions above bigger ones, that seems to tend towards anarchy (a stateless society) - you'd eventually get down to each individual ruling themselves. Or maybe one could argue that we should stop at the city or town level: that would at least be some bounds of people living together in a group. State lines are much more arbitrary - I don't see how one could argue for those being able to decide things on a fundamental level, beyond the fact that the already have the right to do so, to some extent. Country lines are also arbitrary, but there's well-established precedent for national law to override state law in the US, so I don't see a reason to push things back down to the states.

* I suppose if the majority views within states deviate enough from other states, across many issues, one could potentially argue that there should be a split in governance. Agreeing on the best national policy would still be better than this, but you may get to a point where there's too much disagreement for this to work. But this seems to make more sense as a universal policy rather than something decided on an issue-by-issue basis, and it would be less about peaceful coexistence among individuals and more about peaceful coexistence among groups of people with different cultures.

How to peacefully coexist?

Regarding how to actually come to a peaceful coexistence, well, if there was an easy answer, we'd probably already be doing that.

One could argue that there are representative issues with how the government is set up, given the first-past-the-post two-party system, the electoral college, a shortage of laws against bribery, incorporating too many issues into a single vote, a shortage of term limits, etc. But that's probably something one can write multiple books about.

Regarding abortion specifically, I'd argue that the pluralist answer would be pro-choice: allow each individual woman (and her doctor) to make the decision that concerns her and her child, that is compatible with her beliefs and her views on bodily autonomy.

Peaceful coexistence tends to favour freedoms/rights above bans, because freedoms allow you to live consistent with your interests, beliefs, and lifestyles, whereas bans prevent this and involve others imposing their interests, beliefs, and lifestyles onto you. Although one should not have the freedom to oppress others, because that would restrict their freedoms. Some argue that abortion oppresses fetuses while others argue that forcing a woman to give up her body for 9 months to carry around a fetus she doesn't want is oppressing her, and that the anti-abortion view on bodily autonomy isn't applied consistently: we don't require people to give up their organs - even dead people have more rights to their organs than pregnant women where abortion is banned.