But some wallets I couldn't find a "wallet.dat" file, for example the bytecoin wallet was, "bytecoinwallet.wallet"....so I'm assuming that's the same as the "wallet.dat" file correct?
This is not the section to ask about shitcoin wallets. This section is for Bitcoin related questions. Some Bitcoin wallets do not store theirs as a "wallet.dat" file.
Also, maybe a really dumb question, but I'm assuming the moment at which you backup your wallet.dat file isn't stuck in time at that moment with that exact amount of coins correct?
This is where many people are deeply confused. A Bitcoin wallet does not hold coins. A Bitcoin wallet is a collection of keypairs, thus it does not matter when you've backed the keys up.
Say I backup my wallet today and then put in another 10 coins into the wallet and don't back up the wallet.dat file again and my computer crashes, when I reinstall the new wallet on my computer and overwrite the wallet.dat file with the backed up one, does it show the new 10 coins or just the previous balance at the moment I backed up the file?
After you synchronize and rescan the wallet (both of which should be automatic with Bitcoin Core) all funds will show up. It is recommended to occasionally make newer backups though.