For general riding around a city, you wouldnt want anything much narrower than 28mm. Those skinny 23mm are for racing.
I take my 700cx28 on potholed roads, tracks and trails.
A 26x1.5" would give pretty similar performance.

The biggest real difference between a road and an MTB bike is in the forks. Quality road forks in carbon or steel absorb a lot of vibration. Fixed MTB forks are incredibly stiff and unyeilding, and the suspension ones are a lot heavier than fixed road forks.

It is possible to get proper steel forks for MTBs. 26" road touring bikes use them.