Lightroom is also available on the iPad. I hardly ever use it, but I expect that it might be a cut down version compared to the PC/Mac version.
ON1 Photo Raw is also available on the iPad, and it's free. IMO, Photo Raw is one of the best post-processing and DAM programs there is, it's not that different from Lightroom, and it's only £90 as opposed to the annual Adobe subscription. You also get the option of using the free mobile version together with the Mac version, editing on one and getting synced updates on the other for £4.99 per month.
You can check out Photo Raw
here.
In any case, as I said, the mobile version is free. You just import some photos (jpeg or raw) from your Photos app or from a folder on your iPad, edit them, then save them back to your Photos app (Camera Roll) or Share them, including to your Files. It's a little limited in that you can only save 3 file sizes: Medium, Large, and Max, but Max is the same as the full-sized original. Editing includes Crop, Tone, Colour, AI Auto, Details, Presets, Layered FX, Local Adjustments, and Retouching (Healing and Cloning). The one big thing that's missing from Photo Raw Mobile is Digital Asset Management, but that's pretty much the way things are with mobile apps at the moment. Only the mobile version of Lightroom seems to include it, so you could edit your photos in whichever app you like, then import them into Lightroom, tag them, etc, then export them from there. Or sync them to the Photos app and do asset management on the Mac.
And I agree with what RichardC27 says: editing on the iPad, especially with the Apple Pencil, is great for editing right down almost to the pixel level. And sliders are much easier to use when you're not covering them with a fat finger. I use Snapseed as it's very simple and does almost everything I want, and I have a shedload of other apps, including Affinity, for the more complex, once-a-year, stuff.
I hope this is all helpful. If not, feel free to ask me questions.