The answer to your general question, is that it depends on the context.
In my experience doing SEO, for over 10 years, it used to be the case that longer word count was better (not so much that low word count is hurtful, although this is debatable). However, Google's algorithms change and adjust over time to adapt to user behavior, it's ultimate goal being to satisfy user experience, and specifically, search intent.
Since mobile use now outweighs desktop, shorter, more concise text, often satisfies user intent better, and quicker, than unnecessarily long blocks of text/content. The attention span of the average user is typically very short, many want quick answers. Essentially now, there's no real golden rule for content length to rank. It should be the length needed in order to satisfy the users intent.
Specifically, for your situation, however, it most definitely makes a lot more sense to consolidate all of your Q&A on one individual page. Or maybe, you want to have a page focused on specific topics with Q&A. For your example, maybe you would have one page dedicated to SEO, or if your whole site is about SEO, maybe one specifically focused on meta tags, etc.
This approach consolidates SEO equity, and value, into one page, making it more likely you'll rank. You may dilute the value of your pages by having one page dedicated to that specific question.
You can also used structured data for Q&A questions to significantly help Google understand the content of your website, as well as make it easier for them to parse through, and ultimately serve this content to users. Google loves schema and structured data, and in my experience leveraging it as much as possible, greatly helps increase the overall visibility of your content and traffic to your site.
Check out the Google documentation on Structured Data. In your case, it actually seems like you would want to use the FAQ schema, rather than the Q&A schema, as the Q&A one is for Q&A sites like reddit, or even stackoverflow.