a question about ffxiv steam/normal client

[TouchandFeel]

Your player account will work on any version of the game including cross-platform, for example I can login and play my character on both the PC and PS4.
The account and character data is serverside and is therefore independent of the client.

Some of the settings are saved clientside though, such as UI setup, hotbar, audio/video settings, and many of the preference settings, so that will need to be adjusted as necessary.

However when upgrading your version of the game, such as buying the expansion, it has to be bought for the specific version you already own and this includes PC versus Steam version, if you bought ARR on Steam you have to get Heavensward off Steam too.