Moving your cloud data is the biggest headache/hurdle depending on your situation. How much data you
need to extract from iCloud though is not the same as how much you actually have. I'm going with my own anecdotal experience here.
If you use an Apple computer then you might have lots of Pages/Keynote files knocking around for example. Chances are you don't really need to access this on a phone so there isn't much point in moving or converting it all. The three biggest things in my experience are Photos, Books and Notes. Apple offer an iCloud web portal for Android phones but probably by design, it sucks ass.
Photos you can export really easily. Apple built a
cloud transfer tool that will copy all your images to Google Photos in about a day or two, assuming you have enough cloud storage. You can do this in advance of a new purchase. An alternative if you keep all your images stored locally on your phone is to just install Google Photos on your iPhone and backup from there. This does not delete your photos from iCloud.
Books are imprisoned in iCloud. There is no way of moving purchases due to DRM. If you're like me and use it as a PDF library then you'll have to manually export each individual file to local storage and then plonk them in Google Drive.
Notes are a bigger issue. If you use the Notes app for writing then there isn't really a Google equivalent. Their very good notes app, Keep is more of a pinboard than a drafting space. I'd actually recommend taking the time to set up a free Outlook account and start using OneDrive. Its great on your new phone, works on the old one and has a great Mac, Windows and Web app. If you're only ever on a phone a nice homegrown app is
Bundled Notes which is only a $1.30 a month subscription for a solo dev and comes with a great web portal alongside the Android app. No iPad or OS version though yet.
I would strongly avoid using Chrome for your web browsing. The mobile web is a nightmare without a good adblocker. I have found the
Samsung Internet browser (which works on any Android device) to be a worthy replacement for Safari as its extensible.
ABP is a nice way to make the web usable again.
Google sadly killed their own podcast app by rolling it into the not-great YouTube music app. Pocketcasts is a great cross-platform alternative available on most platforms. Apple Music is available as are a great many MP3 player apps. My favourite is ZPlayer because it looks like the old Windows Phone/Zune UX
A lot of this sounds like a faff but I think its important to diversify your data options in case of lockout, price increases or DRM. Android 15 has a lot to love.