Out of the options you mentioned, Pixel with a custom rom (GrapheneOS, CalyxOS, etc.) is probably the best bet. Seconded by any Samsung that could run a custom rom, though I agree with others here that the hardware is better on the Pixels. Plus they have extra security hardware features that will be better. Of course, if things are weird with your telecom, that might effect things (trust me, been there with an Ubuntu Touch phone before.)
Another option you could look at depending on where you are is Murena’s phones. They have a bunch of options pre-flashed with their de-Googled rom /e/ os. Not my favorite rom, but still not bad! And of course those can be flashed with another rom if you want as well!
You can definitely harden operating systems like Windows and Android to be better for privacy and security. I’ve used some of Techlore’s videos to make my Windows system a bit more secure and private, and he’s made one for Android and other OSes too. Of course, this isn’t perfect, but it’s something if you don’t want to install a different OS, it’s better than nothing.
Out of the options you mentioned, Pixel with a custom rom (GrapheneOS, CalyxOS, etc.) is probably the best bet. Seconded by any Samsung that could run a custom rom, though I agree with others here that the hardware is better on the Pixels. Plus they have extra security hardware features that will be better. Of course, if things are weird with your telecom, that might effect things (trust me, been there with an Ubuntu Touch phone before.)
Another option you could look at depending on where you are is Murena’s phones. They have a bunch of options pre-flashed with their de-Googled rom /e/ os. Not my favorite rom, but still not bad! And of course those can be flashed with another rom if you want as well!