Your technical knowledge as described is unironically far beyond the average user so I’d say you’re probably good. Depends on what you want to do though. You can occasionally have problems if you need to do something specific or are married to software that doesn’t exist on Linux. Word processing is down pat. You won’t have the app version of Microsoft Office, but there are open source alternatives like LibreOffice that are compatible with Office file types. For formatting, you may have to download some Microsoft owned fonts since they’re technically proprietary and not bundled with Linux/your office suite. In browser, Microsoft 365 and Google Docs works no differently than normal.
As someone else mentioned, you can test almost any distro on a live USB. There is also this site where you can remote in and test the general look and feel for free. You won’t have an internet connection though:
Threat modeling is simply knowing where potential threats to yourself comes from, and planning accordingly. Most of us have some sort of risk of surveillance capitalism. Companies tracking you across sites, Ai scanning your email and photos, that sort of thing. As creepy as that is, if someone is targeting you specifically as a stalker or trying to break into your accounts, or physically into your home, that will be more important to model for. The things you to to. mitigate one thing may not be the same as something else. Sometimes they can be almost opposite actions, though there are certainly best practices to have in general.
If you know your threat model, you can find guides online of how to plan for it, and you can ask communities online more specific questions if you know what you are asking FOR.