How does it compare to Capture One Pro? I have an old standalone version so it might be nice having something newer with modern features.
Seems too good to be true it being free compared to Capture One and Lightroom.
Affinity Studio, isn't really comparable to Capture One or Lightroom. Both the latter are designed around converting and managing raw files.
Affinity Studio is a graphics editing suite with the photo part of it designed for editing raster files i.e. files that have been processed in a raw converter like Lightroom or Capture One, and then passed, across to Affinity studio for more advanced editing or incorporation into a publication or graphic. But you can ignore the vector and layout tools.
Affinity Studio has no cataloguing tools, and although it has raw processing capability, it hasn't, so far, been as good as the raw processing found in Capture One or Lightroom. Both the latter are more suited to processing large numbers of "related" files while Affinity Studio is more suited to working on "special" files one at a time.
As Affinity Studio is free, I would try using it alongside Capture One. Keep C1 for raw processing and cataloguing, but with Affinity Studio available for more advanced masking and retouching (along with the additional vector and layout graphics tools) should you need them. Even though I have the latest release of C1, I still find things that are just easier and better done in Photoshop, and the Photo part of Affinity Studio is comparable to Photoshop.
The free version of Affinity Studio doesn't include the AI tools for things like object selection that you get with the paid version, but it still has basic object selection tools. And both AI selection and object selection are likely to still need tweaking: you just save a bit of time with the AI.
The more recent versions of C1 have been adding AI tools. The earliest was an AI horizon correction tool, followed by AI dust removal, but it now has a slew of AI driven selection tools (and people retouching tools) including the ability to add, subtract and intersect masks.
How old is your version of C1. C1 has seen a lot of additions over the last few releases, but it is still a very expensive option.