Recently a JSON-LD for SEO customer was asking what other SEO apps I recommend.
You can use other Shopify SEO apps but I recommend sticking with Shopify's built-in SEO features.
Years ago Shopify's built-in SEO features were weak and themes didn't do a great job either. That period had Shopify brushed with the "poor SEO" brush.
Now Shopify's SEO features have improved a lot and most themes have good quality defaults that compliment them (your theme choice is easily 50% or more of your SEO features).
The problem is that most people don't use or even know about some features. So they go shopping and end up buying something they already have (e.g. bulk editing SEO titles for products, alt tags, sitemaps).
On the apps side, a lot of the SEO apps add unnecessary code and I'm always finding data or coding bugs in them.
I've lost count of the number of times an SEO app has destroyed a store's ranking and search results.
There are quite a few non-Shopify apps that are useful. They are the scanners, keyword researchers, and crawlers. All stuff that should be done outside of Shopify and where you want to go with one of the industry-standards.
I cover a few in my Shopify SEO article.
But Shopify specific apps? Best to run lean: a product reviews app, a decent theme, and a structured data app like JSON-LD for SEO.
Anything beyond that will need to really prove its value and safety.