SafeERC20 and SafeERC20Upgradeable are the same. The reasons we rename it are 1) to make it clear that the code is safe for upgradeability, and 2) to avoid potential clashes with the original one.
You can use either. If you're using the Upgrades plugins to check safety (which you should), then this is ok. If you're not using them, I would recommend sticking to the Upgradeable variant because it gives you a better guarantee of safety.