Layer similar "questions and answers", but allows you to only vote for a topic, without the possibility of voting for answers. Also in the list of forums not displayed the number of responses, and visible only to vote for the topic.
If the feature is implemented, then displays "done".

In the attachment screenshot. I think that the implementation will not be difficult.
The fact that I couldn't find a good plugin to collect votes requested features when developing software.

Even if such opportunity will be as an addition to the plugin, we are ready to pay for its implementation.

Please note, only the first post (topic) votes are counted and displayed on topic list [ votes ] section. The answers votes are not included in the statistic. This is the exact what you're wanting. You don't even need to hide answers voting buttons, they are not being counted.

To disable Answers on topic list you can use a simple CSS code. Put this code in Dashboard > Forums > Settings > Styles > Custom CSS Code textarea. Save it, delete all caches and do Ctrl+F5 on forum front:

#wpforo #wpforo-wrap .wpfl-3 .wpforo-topic-status .answers{display: none;}

 Sorry for my English, I use translator. Maybe something wrote wrong, I meant.
I know that only a vote for the topic affects the counting of votes, but users do not know and can vote for the answer by mistake

Using your hints I achieved what I wanted. Here is the CSS style that I use. But if I issued a "voting system" in a separate layer, it would be much better! =)

#wpforo #wpforo-wrap .wpfl-3 .wpforo-last-topic .answers{display: none;}
#wpforo #wpforo-wrap .wpfl-3 .wpforo-topic-status .answers {display: none;}
#wpforo #wpforo-wrap .wpf-answer-wrap .wpforo-post-voting {display: none;}
#wpforo #wpforo-wrap .wpfl-3 .wpforo-post .wpf-right .wpf-add-comment-button {display: none;}
#wpforo #wpforo-wrap .wpfl-3 .wpforo-post .wpf-right .wpf-answer-button {display: none;}

The result can be seen here:  https://gbsmarket.ru/community/main-category/