The Android experience is quite a bit more wanky than Apple's walled garden. I moved to Android a year ago and it took me months of fiddling until I was satisfied. Google really tries to give you their own not-that-walled garden, giving you an Apple-esque experience. If you are not 100 % invested, it could get finicky, though. The vendors usually provide their own standard apps, but more often than not, I find them unpolished.
Regarding Log in with Apple, you could, from what I experienced, get problems, as some Android apps won't let you sign in wit Apple, and even websites don'support it all the time. Take Tripadvisor as an example. Create an account on the iOS app, and when changing to Android, you're basically locked out, because neither their Android app nor their website support Log in with Apple.
I went the /e/os way and quickly turned back. Not to dismiss the effort of the maintainers, but it really felt like a frontend on lineage os meant to sell alternative cloud services. I did not find convincing arguments over a bare lineage os and the pretty much forced /e/ cloud was a total turn off.
I went the "real" security / privacy way and switched to grapheneos. Very happy overall, already went thought with 2 major os updates, no issues whatsoever. Only issue would be if you want Google pay (won't work on graphene). You'd need a pixel phone if that's in your budget. The pixel phones are great at photos, but pretty "meh" otherwise
for the first point, Transmission has a pretty serviceable web client that works great on iOS as a web shortcut
its just occurred to me you might mean downloading torrents directly to you iphone, rather than a remote to some other device.... in that case a web client isn't sufficient, you'd have to sideload
You can actually (indirectly) torrent on iOS via seed box. I use SonicBit, which has an iOS app. I find it’s actually more convenient than torrenting directly as the files are stored and seeded online yet still accessible to me when I need them. Then you can download the files to your iPhone/iPad.