AppFollow is well suited if you only operate in a few app store countries and don't have a high volume of keywords that you are looking to rank for. This is, of course, the free plan. Besides that AppFollow is well suited for communication with other apps - they have an open API and other connections to a ton of third-party analytical tools.
While App Annie is extremely robust and pulls in data from acquisition channels, app stores, and elsewhere, it can be quite overwhelming at times. If you are looking for more simple and just keyword positioning then definitely look at AppFollow. Apart from the two platforms themselves, I've had numerous contact experiences with both AppFollow and App Annie. The winner is definitely AppFollow with a less aggressive approach and a higher willingness to go above and beyond to make sure all questions are answered. With App Annie I was bombarded with a ton of sleazy, sales emails to purchase their product.
Semrush's content and page optimisation tool is quite poor; it's not in the same bracket as Surfer. Frase is a good alternative from a cost perspective (if not paying the AI writing functions), it's cheaper, and Frase's keyword/topic heatmaps are quite unique. Sufer has a better UI and a shorter learning curve. It has an advantage in that it offers internal linking recommendations, which Frase lacks. Surfer also has limited competitor analysis (backlinks and page speed), which Frase does not. Both tools allow you to choose the number of competitors on the SERPS