I'm afraid we're in a bit of a state of limbo on this issue, Nickington.
Currently, Google's ranking is based on the desktop version of the site for both desktop and mobile results.
Google has clearly stated, and many tests have confirmed, that content which is not visible unless a user interacts with the page (such as having to click the drop-down for the FAQ result) is deemphasized in search results.
BUT! Google has also stated that they are in the midst of changing to a mobile-first index which will mean that the mobile version of websites will be used for ranking assessment. In addition, they've been quite clear that at that point, since things like accordion drop-downs are so much better UX for mobile users, that kind of hidden content will no longer be "penalised".
Unfortunately, there's been no declared date for when the switch to the mobile Index will occur. Instead, they've said that it will be rolled out gradually to individual sites as they detect that the mobile version of a site is ready for it. This means it's entirely impossible to assess when the changeover might apply to your site.
So for absolute best SEO, the solution is unfortunately a bunch of extra work for a hybrid solution My best recommendation would be to build out the FAQ content using headers and sub-headers so the content is fully visible on the page and gets full indexing authority from the search engine. Then keep an eye on the mobile indexing of your site to detect when it appears that it has moved fully into the mobile-first Index stage, and at that point redo the FAQ page to utilize the accordion drop downs instead.
The alternative would be to build out the page using the accordion drop downs to start with, and accept the fact that it will be some time before that hidden content has a chance to rank effectively. this would definitely be a second-best option in my opinion.
Does that all make sense?
Paul