Moving topic to another forum is handled automatically in the current version of miniBB. Whatever forum is used, whatever topic is moved. You could use Muliple Topics Action tool or move topics one by one :) It doesn't matter. Moving one-by-one means you could check at least one/some of them.
Right these days we're working at the Elvis tool, which I described shortly in my random blog
. With that you would be able to check any URL for the status it gives and the URLs it redirects to; also much more. But this is not ready yet... you may search Google
which results provide something similar for free for being sure moved pages give 200 (OK) status.
Once that is complete should i delete the forums i no longer need? or will this effect the redirecting?
From what we have coded, it should not affect redirection even if you remove the older forum.
The most important is the topic's ID. The script will look up for it in all possible places, incl. Archives
. If it's not found, then it will give 404 (in the current version; in the upcoming version it will give 410). So the forum's ID should not matter for this case.