Q. WILL IT BE COMFORTABLE TO RIDE FOR 5.3FT HEIGHT PERSONS - Imperiale 400?

The seat height is 780 mm, as compared to the RE Classic 350, which is 800 mm. What you need to consider here is your inseam length, not your overall height. Even if your inseam length is a little less than 780 mm, wearing riding boots with a thick sole May make you feel more comfortable. Also, riding boots are an essential safety gear that will protect feet in a crash. So, what I would recommend is, measure your inseam, then wear riding boots and take a test ride.

My height is 5'4 and i ride imperiale 400. Theres no such difficulty in handling bike. but in city traffic it feels heavy bike . But with experiance i can manage it with ease.

Difficult to answer. If you find the Royal Enfield Classic comfortable, this will give the same experience, since the seat is slightly lower.