Yes, you can use Squirrly SEO alongside SEO plugins in compatibility mode. You can learn more about how to use Squirrly SEO in compatibility mode here.
If Squirrly stops handling source code changes, then it works with RankMath, SEOpress, SEO Pressor, AIO SEO, Yoast, and others.
Basically, you can use Squirrly SEO to power up WordPress on top of everything that is already handled by the other SEO plugin you are using.
Of course, you can also decide to switch to Squirrly, as it offers the complete SEO funnel. Check out this resource to see how Squirrly compares to other SEO plugins such as Yoast, RankMath, SEOPress, and All in One SEO – and hear from other users who’ve made the switch.