The iCloud app works well for me.
I have the cheapest paid option for iCloud storage, 50 GB for $0.99 monthly. This takes care of storage and backups for two iPhones, an iPad, and a MacBook Pro. It’s awesome for when it’s time to upgrade a phone: activate the phone on your account, and it automatically sets up your new phone using the backup. For long-term storage, I use an external USB drive on my PC.
I installed the iCloud for Windows app on my PC. With it I can download files, pictures, etc. from iCloud storage to my PC, then save them locally on the external drive. Afterwards, I remove the files from iCloud, freeing up storage space. I haven’t tried moving files from PC to MacBook or iPad using iCloud, so can’t offer any insight or advice, other than it’s probably just as easy.
I don't do cloud computing. I backup everything on external drives, then drag & drop the folders onto the new computer.
I've been doing this since the mid 1980s. Owned ten computers so far. I've backed up on 5.25" dics, 3.5" discs, 40MB external discs, and external hard drives of ever increasing sizes.
Every month or two, I attach one of my external backup drives to my old, backup laptop, and transfer the new files onto it for additional backup. Copy over the AppData folder so all my emails and browser bookmarks are backed up too.
I always keep one backup drive in my bank's safe deposit box, in case there's a fire at my home.