The changes to the control panel are an annoyance, although they're much less annoying than the similar changes to 8/8.1

I don't like Edge, either, but going back to IE seems even worse. You really can't tolerate either Firefox or Chrome?

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Assuming for a minute that the right solution might be going back to Windows 7, why do you think Pro rather than Home (Home Premium?) would make a difference?

As for the new PC, whether it will run well on Windows 7 depends on the hardware. Most new PCs are still capable of running it, but there are a few features (mostly higher end stuff, or on hybrid tablets) which will be problematic with Windows 7 -- most of which will simply be happily disabled [e.g. many Thunderbolt ports] but systems that have ONLY USB-C based ports or which are touch-related (including some newer touchpads) may cause problems with the functionality in general.

It's also very much a "wipe and reinstall" -- there is no in-place downgrade unless the machine was manually upgraded before.

I actually like the Microsoft Calendar app.

Weather and News, not so much. Easy enough to get rid of the tiles, may even be possible to uninstall the apps.

First step is to have a Windows 10 Pro retail license, or a Windows 10 Pro OEM license from a manufacturer who has a contract that allows downgrades.

Home has no downgrade rights.

Costco has a very liberal return policy. Of the major manufacturers, they're the last one I'd consider.

Definitely works with retail keys. Not sure if it works with OEM keys, but the worst case scenario -- doing the upgrade and then having it not activate -- is readily fixed by doing a backup first (and I think the rollback feature on upgrade will actually save even that much trouble, should it happen.)