Will you mostly work via the mobile app in this case?
No. Sugi Card is a hardware wallet and the Sugi Wallet is the mobile application which can be used as a interface for hardware wallet and/or standalone software/hot wallet. You must use the Sugi Card with the Sugi Wallet in order to have the hardware wallets functionalities- wallet is a mobile application which provides easy to use interface so you can manage everything that is on the card. However, if you dont own a Sugi Card, you can still use the Sugi Wallet as a standard software wallet by creating virtual card in-app that holds your cryptocurrencies- for example to initiate smaller transactions or store smaller amounts of cryptocurrency.