I'm sorry but we're not familiar with this plugin and we cannot answer on this question. You can ask this question the plugin developers as well.

I am already getting some indexing

But can I still add rankmathpro... or  just other pinging plugins like Bing url Yandex et cetera.

Just improve thing...

My main question is does pinging and url submission  plugins work on wpforo when new topics are created? 

wpForo has its own pinging system (function ping_search_engines()) with the forum sitemap. So it'll be indexed as soon as possible. Also, make sure you've inserted wpForo sitemaps into your Google Webmaster Tools. The forum sitemap URL can be found in Dashboard > Forums > Settings > General Tab. Here is the wpforo.com sitemap: https://wpforo.com/community/sitemap.xml

I am running wpforo as a standalone, and I need quick indexing.

In the past my post get index within 3 days due to rankmath auto ping and instant Bing index it contains... But with wpforo it taking time.

I have read about rankmath and wpforo questions while finding answers and I found out that rankmath seo won't function on wpforo pages...

But I want to know will  apart from the seo parts which I feel wpforo has handled... Can rankmath detect the  creation of new post in wpforo? Which therefore helps to ping to search engines too?

Can auto ping booster or Pingler work on wpforo.... Just to ping the search engine faster...

I have seen that a code in wpforo nullify rankmath "seo" ... Bravo!

But does the pingings and instant indexation still functions?

Note that the rankmath uses the same site map wpforo generates...

Rankmathpro

Needs quality answers ASAP