Tbh I think disabling play services on a Samsung phone is kind of like pissing into the wind since Samsung's privacy is so terrible, but I guess it's better than nothing. Only one company stealing all your data instead of two lol.

Maybe it's because I haven't used One UI and I'm misunderstanding what you're saying, but I'm pretty sure some of those aren't really much different on GrapheneOS (or AOSP). Brightness can be changed in the quick settings/toggles/whatever they're called thing in the notification shade using a slider. Bluetooth autoconnects when enabled, although idk if there's a way to get it to work on the lock screen without unlocking. There might be a setting to allow it. I personally don't think it matters much since it's not like I constantly turn it on/off. It also takes two taps I guess if your phone is already unlocked. IIRC the wifi/cellular thing is fixed in Android 16 QPR1 (so will be fixed in GrapheneOS soon), but I haven't checked recently so maybe that changed.

The Google search thing is not there on stock GrapheneOS since it's not using pixel launcher or whatever. Idk when you last used it since you mentioned the Pixel 5, so it might also just be things have changed since you last used it.

I'd be pretty much fine with the USB-C dongle solution if there were two ports, but there aren't so you need to pick between charging and headphones, which is super annoying. Phones with headphone jacks are basically dead though now, unfortunately.

Pixel hardware is kind of a mixed bag though, yeah. Beyond the headphone jack issues, the kinda shitty processor (compared to Qualcomm) is irritating as well. Doesn't usually cause problems, but games or even just flutter apps sometimes just run poorly. Samsung hardware with GrapheneOS would be my ideal phone probably.