Suggestion to be more constructive, you should share your code maybe open a Mod topic in the Mods forum. I'll do the same later if the request is worth it.
I use the WordPress Execphp plugin to import the vBulletin topics of each forum into WordPress.
I'm now on PHP 7.2+. I have to double-check the vB-WP bridge because I have a fatal error under this version of PHP. I won't have time for several weeks. My priority is the vBulletin side right now. WordPress is after.
For the UTF8 :
https://vborg.vbsupport.ru/showthread.php?t=327461