Proxy servers are good for bypassing censorship, but do very little for security or privacy and also don't reliably hide the fact you are using Tor. If you want to use Tor without it being obvious, then you should look in to Tor bridges with pluggable transports.

For most users, yes, but you can quite happily root a smartphone and install an open source OS on it such as GrapheneOS or Ubuntu Touch, along with a non-google app store such as F-Droid. It's perfectly possible to de-google all your devices (and for free), you just need to have the motivation to do so.