I don't see a reason why you couldn't. You could just make two partitions of the external drive: one for your Linux install, the other for a backup. Then in your BIOS you could boot from the Linux install. A bit technical but if you talk to MapleAI or nano-gpt about it they could probably give you a step by step.
Those are some of the best applications for privacy tech. Beyond that the best password manager is KeePass. Best browser against fingerprinting is Mullvad Browser (Tor browser without Tor). Its the only desktop browser that consistently fools fingerprint.com for me. Don't sleep on Tor Browser for daily use too, it has great privacy protections vs even Mullvad + VPN.
Speaking of VPNs, Mullvad or NYM are the best right now no question. Both go beyond simple IP obfuscation and mask packet fingerprinting which is a huge privacy boost.
Another thing to look into is an OpenWRT router, like the OpenWRT One. You just use it instead of your ISPs router and because the firmware is FOSS you have no spyware, higher performance, and can add a router level VPN, custom DNS, and more privacy features. I'd say don't worry about that yet your OS choice is most important I'd focus on Linux and GrapheneOS for a while until you're feeling the itch to go further again. Important not to get overwhelmed, never let perfect be the enemy of good.
Can't think of much else you're going really deep into it which is incredible I'm quite impressed.