VoiceOver for third-party apps

I’ve been thinking of upgrading my grandparents’ Mac. They were quite happy with it, but I guess it’s time to do some adjustments.
However, there is another thing to consider. My grandmother is 83 and her sight has been declining for some time now. In fact, she is low-vision now and it became hard for her to navigate the interface in a usual way she did before.

She is well-versed with the keyboard, however, so with the touch-system she handles emailing pretty well. FaceTime goes fine, too. I occasionally send her audiobooks and links to podcasts she might enjoy and some music quizzes to entertain her.

If something goes wrong preventing her from opening the attachments, grandpa is there to help her. That is, to be her eyes – she is more tech-savvy that he is. She used to be a programmer when they used to feed the punched cards into huge computers. She changed occupation after giving birth to my dad, but I guess if you have a knack for something, it’s forever. Therefore, I’d rather she could do everything by herself, as she grasps all the tech things fast enough. It’s just her sight is not what it used to be.

I’ve been also thinking, of some apps that might be good for their Mac, like <a href="https://getpocket.com/">Pocket</a&gt; to save articles, <a href="http://spotify.com/">Spotify</a&gt; for music, <a href="https://macflypro.com ">MacFly Pro to deal with</a> clutter and old files, and so on. I use them and think that they would be simple and user-friendly enough for my old folks. However, I have my doubts about their compatibility with VoiceOver.

Is there any way to know whether an app is compatible with VoiceOver?

Does VoiceOver work with third-party apps at all?

Are there any other apps that might facilitate the transition? (all I can think of is various magnifying tools, but there must be something more.)

Thanks!