I prefer to pay for a better experience, as long as the price is reasonable to me.

Have you got an official source to confirm that?
As far as I'm aware the single player campaign of Gwent will be offline (and entirely separate from the multiplayer part, so no need to check your account or anything).

Actually it's quite common, most mobile online free to play don't require you to log in.

When you install the game you are assigned a unique token and this token is used to identify you, it's also used if you do purchases.

Most games also offer a real "log in" feature (e.g. use to your facebook credentials, use your google play account, etc...) but it's optional.

That's why for those games if you uninstall and reinstall the game you lose everything; all your progress, all your purchases and you restart from zero. (of course if you made purchases you can usually contact the game support to "recover" your old information)

Can you give me an example of a 100% online free to play game that doesn't require a log in?

Unfortunately your fighting a lost cause. There are a group of gog defenders who will deny this to the end. "It's free, therefore not drm", "it's built with that as a fundamental part, therefore not drm", "gog promised an offline version at some point in the future, therefore it's drm free", etc. All been said before and the simple fact is, if I was happy to get products which require always on internet I wouldn't be shopping here, call it drm or whatever you like, it's third party control of the product.
And don't forget goblins inc. another one on the edge, or the recently announced absolver, which states in its video online only, it's a growing trend and all part of the "steamfication" of the site.

Well :

Tales of Link
Fate Grand Order
Shadowverse

etc...

Like I said most of the Mobile F2P don't require a log in.

How do these games identify you when you return to them?

Installation data, uninstall the game or clear the application data and all your progress are lost and you restart from zero. (Unless the game support team is nice enough to recover your data)

Actually that's sometime something "useful" at it allows re-rolling, something very common with "gacha" based games. (As your units are chosen randomly from a pool, it can be useful to "re-roll"/"restart the game" until you get strong units.)

Usually most of those games allows you to generate a "transfer code" that originally is supposed to be used when you change your phone but can be used as a way to backup your "account".

Some games also allows you to "link" to your Google or Facebook account if you want to be safer but it's optional.

...so they do have a login of sorts, but it's a login that is locked to one device, and is out of my control (unlike a password and username that I can choose to enter if I want to) and you think this is somehow better?

As mentioned it's not tied to a device but to the installation data (think "save game"), as if you clear those data it will consider it being a new connection.

Never said it was better or worse, just said it was possible to have an online F2P without needing to login and/or create an account and that it was actually quite common with mobile F2P.