As to the third part of your question... there can often appear to be a correlation between some of those offerings and improved site metrics which could be signals for improving organic rankings. But there is no definitive cause and effect that I can point to that would say "yes, always put these in" or "no, they never work." More specifically, having legitimate and useful reviews can help improve user engagement and can help to improve conversion rate. Having a decent amount of reviews can also allow you to add schema markup to the page that can add star ratings into your organic results which could improve your CTR. Will it always do this? No, but it can.
Videos are also a good way to improve user engagement, if its a decent and relevant video. Especially useful if people like it enough to share it either because its incredibly informative on the relevant subject or really amusing. This increase in time on page, lowered bounce rate, shares, etc. could improve organic rankings but there is not always definitive proof that this is the case. Videos can have the opposite issue as well... sometimes they just want their question answered or the information presented to them instead of sitting through your 2 minute video about the product offerings or how to install it.
Good images is just good business and so are good descriptions. Having relevant images on your page can also help you take up real estate in image search as well as generic organic SERPs. Having an informative description can help with a variety of ranking signals. But you need to make sure that you are not going overboard, stuffing keywords, or attempting to game the system. For some people, adding 5 images with great, informative descriptions could be helpful. For others it could be 10 images. But for some, those 10 images could wind up inadvertently hurting them if they don't things according to best practices.
Highlighting relevant blog posts? Well, that could help with retention on site as people are more likely to find the information that they need quicker and easier. Promoting flow through your site to the right information is a plus to UX which would make people more likely to come back to your site or to suggest this site to other people. It could also help with the flow of link equity to relevant pages that would then benefit from the infusion and possibly rank better. Or if overdone, or not done properly, it could have no effect, little effect, or the opposite effect as you clutter the page with extraneous links or dilute equity by pointing links at irrelevant pages.
Email subscriptions. This won't necessarily have any sort of organic impact but can help in the retention of users who are then slightly more likely to return as direct visits.
If you're looking for a magic bullet to increase your rankings via user engagement, there is no such thing. There are things to consider best practices and things that work for the right types of sites and things that work well if done properly.