For the specific scenario you outline (theft of your computer or hard disk), that will probably work. Note that EFS is based on your Windows password, and Windows' password hashing is incredibly weak by modern standards, so your password will need to be extremely good to prevent a dedicated attacker from brute-forcing the hash.
Additionally, EFS provides protection against a malicious (or compromised) program running in another user account on the same machine. If you care about that threat, then EFS is probably the way to go. However, be aware that EFS leaks some information about encrypted files (specifically, the file metadata like access time, file size, and so on) so make sure you don't care about that if you use EFS as your only layer of encryption.
A better option if you don't care about the same-machine-cross-user threat is BitLocker volume encryption. Although originally only available on the most expensive Windows editions and requiring hardware support, these days I think all Windows editions that support EFS also support BitLocker, and you can skip the TPM by using a boot-time password. This password is hashed far more securely than Windows user account password hashing. Additionally, BitLocker will also protect all the other sensitive data you might have outside of your web browser, like passwords/tokens stored in other desktop apps, documents, and multimedia files you keep electronically, and so on. There are lots of guides online for doing this; https://www.howtogeek.com/howto/6229/how-to-use-bitlocker-on-drives-without-tpm/ has a pretty good walk-through.