Is Chromium's behavior any different from Chrome's sync. behavior?

Years ago, I started using Chrome instead of Chromium or Firefox because they made Flash work out of the box on Linux. Although Flash is not important for me anymore, I just never looked back.

With all this new strange Sync and Log-in behavior, I'll might change to a different browser.

Because the large majority of users have no idea that there are alternatives, or are scared to switch because they are so locked into the whole google ecosystem.

This is one reason why I like Brave. It has the Chromium engine, but less Google glut. Mind you they have some funky stuff going on with Brave rewards. But thus far, I have very few complaints.

I'd use it, but where are there installers that 1) I can trust and 2) are updated as soon as Google releases a new version and 3) that allow me to get automatic updates (without having to check for an update .exe myself)?

I don't know about Windows, but it's available on pretty much any Linux distribution. I don't know if that's an option for you, but if you're worried about Google, you should probably be worried about Microsoft too.

I halfway agree with you but one company sells you and the other sells you products. Microsoft and to some extent Apple are not the best companies at times but they are not in the same category as Ad companies (Google/FB).

"but one company sells you and the other sells you products"

Those activities aren't mutually exclusive, especially when first one can help the second (example: Win10 telemetry).