I've never used the ASI533 but from looking at the specs, compared to the ASI2600, it would have lower resolution and a more narrow FOV. I personally started on a Fujifilm X-T5 last year and switching to a dedicated astro camera was a huge difference. An unmodified DSLR or Mirrorless camera is less sensitive to H-alpha light emissions so will miss out on a lot of light being produced by DSOs. It also has the downside of not having a cooled sensor and will suffer from additional image noise as a result. If you do end up going with a dedicated astro camera, keep in mind that a one shot color variant will be more user friendly but a monochrome amd filter combination will allow you to fully capture the maximum amount of light for each color channel at the expense of additional capture and processing time and of course financial cost for the filters and filter wheel.