For the laptop, you can leave it with Windows but don't use it for anything except what requires Windows (e. g. don't use social media or store private photos on it). If you use it very often, consider dualbooting.

For your phone, make sure you use a custom ROM. If you need Google apps, there's stuff like microg (sandboxed Google apps that are either pre-installed in the ROM or you can add it to a ROM that doesn't come with any Google apps by default). Regular Google apps are very invasive and stock ROMs are even worse because they have their own telemetry. But I wouldn't recommend using obscure ROMs (especially unofficial builds).

There can be an issue with banking apps though. Recently Google replaced old SafetyNet system (which checked the system for root and unlocked bootloader) with a new one called Play Integrity. The problem with it is that 99% of custom ROMs can't fully pass Play Integrity so apps which require it (mostly banking and government apps) won't work. Also Snapchat and WhatsApp started banning custom ROM users recently. The only reliable way to avoid these issues is to have 2 phones: one on stock unmodified ROM (for banking apps and other things that require Play Integrity pass) and a degoogled phone with a nice reliable custom ROM (LineageOS and GrapheneOS are my recommendations but you can look at other ones like crDroid if you want more customization features). It can be a bit inconvenient but that's what you probably need if you want really good privacy