To your point about tinkering, GrapheneOS has an excellent web installer. CalyxOS has a fairly decent install procedure but is maybe slightly more involved.
If you want to make a move in favour of privacy you might want to ditch the smart watch you currently use if it's a proprietary system that also leverages Google play services, as your health and biometric data is also very valuable to these companies.
Regarding root, I feel as if root access has been more or less phased out in custom ROMs today, likely for attestation purposes but I suppose also to prevent end users from causing irreparable system damage.