Triumph Scrambler 400 XC

Taking your considerations into account, bikes we would recommend taking a look at are the Triumph Speed 400 and Scrambler 400 X / XC. 

Both will offer you considerably higher performance than your Yezdi bike and will also be comfortable enough to handle daily commuting duties while being brisk enough on the highway as well. 

If you want an air-cooled, torquey engine, then you could even take a look at the Harley-Davidson X440, which is a comfortable neo-retro roadster that has decent performance. 

Take a test ride of the machines you shortlist before picking one. 

Of the options you've shortlisted, the Royal Enfield Himalayan 450 will be the best all-rounder with good highway manners, plush suspension for rough roads, and it's usable inside the city too, although its weight and general size need to be kept in mind. 

The Meteor 350 and Triumph Scrambler 400 XC will be better in the city than the Himalayan, but out on the highway, your comfortable cruising speeds will be capped at 80-100kph. Take a thorough test ride before you decide.

You can definitely learn on a Triumph Scrambler 400 XC, as it's a very forgiving 400cc 40hp machine; however, we would steer you toward the Hero Xpulse 210 instead. 

Considering you're also going to do some off-roading and you're simultaneously also going to be learning to ride a motorcycle, the Xpulse is a more forgiving machine than the Scrambler 400 and will be a better fit for city usage as well.