if you want to degoogle the only way to run some apps without unprivileged code (GMS/microG) is to use grapheneos & its sandbox compatibility layer. this is unfortunately only available on the pixels.
I also worry you won’t be able to use some of the customization options that the nothing phone 2 offers with its hardware when using a custom ROM. if thats something u care about.
I have the pixel 7a & have had essentialy no issues with anything for what that’s worth.
have you considered using alternatives front ends for some of the major social platforms?
I use libreddit/redlib to browse reddit. you can run an instance locally or connect to remote ones. this way your IP isn’t logged by reddit in the first place & no JavaScript is required to be run for the website to function properly.
there is even an extension called libredirect which can automatically swap clicked reddit (& other platforms) links to the same page on public frontends, which removes the hasstle of manually changing the URL.
self hosting is the only way to guarantee logs arent shared.
however it also means that your server address only pulls requests for things YOU look at, not the whole pool of people using the server. imo this is a bad trade off as it would allow the services to track my browsing easily anyway.
personally I would recommend looking at libredirect with a large # of frontend instances selcted & a vpn/tor. these websites normally work without javascript, so assuming you have a privacy focused browser your IP is the only tracking metric they really have. spreading your requests out over different servers whilst using a proxy would make this really difficult to correlate as it would require that mutliple instance operators were malicious & collaborating.