Yes. It’s still in beta because I wanted to wait a while for some people to test the version and give feedback. So far I didn’t get any feedback so I assume that either nobody uses v3 or everything works fine 
There are some issues and pull requests I want closed before the stable release, too.
You can send everything you are comfortable with. But try Uniform v3 first, it will probably work better.
Yes that should be fine but with Uniform v3 there is only a single CSRF token per request/page so you won’t need multiple tokens. Just make sure you generate the token only once for multiple forms:
<?php $token = csrf() ?>
<form>
<?php echo csrf_field($token) ?>
</form>
<form>
<?php echo csrf_field($token) ?>
</form>
You can also implement one dedicated route for each form so you don’t need that _id stuff any more.