After this update... will it still be possible to use LEGACY addresses normally? And also create raw transactions in the same way as we currently create?
Of course you still can, because this is a soft fork, which means that existing consensus rules and protocol are preserved. It's only *adding* new functionality to it.
It's not like they can mandate everyone to use Taproot addresses anyway.
These days, it does not make much sense to use Legacy addresses (1xxx...), even if you can. You should be using at least wrapped segwit legacy compatible addresses (3xxx...), but even better are the most recent segwit native addresses (bc1qxxx...)