I was in a similar situation a few years ago, and I failed to recover the coins despite trying everything I could. I received some altcoins as a bonus for my work and forgot about them. Later during the 2017 bubble the price of those coins skyrocketed, and I tried to access them, but couldn't find the wallet file on my computer. I used hard drive recovery tools and found some wallet.dat file, but it was corrupt and couldn't be opened. Looking at hex dump, it looks like large parts of it were already overwritten by other data.
So, generally recovery will either be very easy if you have the right password and wallet, or effectively impossible.
No, what you need is the seed words for each wallet, nothing else.
You are supposed to write those seed words down when you create the wallet, and store them in a very secure place. Preferably then make another copy with your own hands and store that paper in another, physically separate secure place.
If you fail to do that, you are bound to lose your coins. Neither the password no the wallet backup are important, the seed words can regenerate the wallet, anywhere, passwordless. The password is simply something to keep the wallet encrypted while in use, or someone casually using it while you go a moment away from your desktop. Its not needed to recover access to it as long as you keep those words.
The older wallets wouldn't show you the seed words but could export the privkey, which when printed, could more or less achieve the same. But that is much easier to steal, so it has fallen in disuse. No one should be directly handling private keys, only seed words.