What is currently THE gold standard for individual bitcoin security?

Suppose John owns several whole bitcoin (don't bother PMing me, I do not, John is hypothetical).

John has everything under control physically - he doesn't talk about bitcoin publicly or post about it online, his house has a decent security system and he doesn't post vacation photos to advertise being away. His seed phrase his is written on a steel card hidden somewhere within his house that would be nearly impossible to find (and he has also memorized it). Only his spouse knows the seed location and they are careful of any tradespeople or visitors being in the house unsupervised.

Supposing John's seed is being kept secure, what should he be doing in terms of hardware wallets, phone and computer security, passphrases, MFA etc. to ensure his bitcoin is secure? John is not a corporation so doesn't need the same protocols as something like MicroStrategy, but holds enough that it is worth spending a bit to make sure it cannot be compromised.