Since you have a commute that has some highway riding, we'll recommend bikes displacing 250cc or more so you can maintain decent highway speeds without feeling the engine is strained. 

There are loads of options in your price bracket, like the Royal Enfield Hunter 350, TVS Ronin, Honda CB300F, Bajaj Pulsar N250, Hero Xpulse 210 and TVS Apache RTX 300. 

Take a test ride of all the machines you shortlist before going ahead with your purchase. 

Of the three bikes you're considering, the KTM 250 Duke will be the most engaging handler, but it has the least peak output and the smallest engine. This means you will have to rev it more to access the meat of the performance.

The Triumph Speed 400 is the most powerful bike of your shortlisted options. It will be a great city bike because of its effortless performance and plush suspension.

The TVS Apache RTX 300 is sure to be the most comfortable machine of the three. Its long-travel suspension and commanding ergonomics help, but it is also the tallest and heaviest bike on your list.

Take a test ride of all three to see which one fits your needs the best.

Considering your use case, we would advise choosing between the TVS Apache RTX 300 and the Hero Xpulse 210. The RTX is an adventure bike, which will make it great on the road, while the Xpulse is a dualsport, which will be more capable during serious off-roading. 

If you want a more road-biased machine, then the Honda CB350 H'ness (or either of its siblings), the Royal Enfield Classic / Bullet 350 and the TVS Ronin would make for a good option. 

Take a test ride of these machines to help decide which one is best for you. 

Since you have mentioned you want a powerful motorcycle, we would recommend you look at the Triumph Scrambler 400X, KTM 250 Adventure and TVS Apache RTX 300 in the ADV / Scrambler category. Of the three, the Triumph bike is the most powerful, but it is also pleasantly usable inside the city, whereas the KTM and TVS are more do-it-all machines that will also be wonderful on a day-to-day basis. 

Coming to the Xpulse 421, there's no official communication from Hero on when it will be launched, so we would recommend going with any of the other options you are considering. 

Take a test ride of whichever option you shortlist before you choose. 

If you are comfortable with the heft and size of an adventure bike, then the KTM 250 Adventure and the TVS Apache RTX 300 are both sensible, smooth and comfortable options. Between the two, we'd recommend the RTX because it gives you more for your money. 

The TVS Ronin is a fantastic bike too, with a smooth engine and good comfort, so if you want something lighter and more manageable that's also easier on the wallet, you can consider the Ronin. If you're open to the idea of owning a Royal Enfield bike, then the Hunter 350 will also serve you well because it is smooth, comfortable and reliable.

We recommend a thorough test ride of all machines you shortlist before you make your purchase. 

If you are comfortable with the size and heft of the TVS Apache RTX 300, then it is certainly worth considering because it will fit your needs quite well. 

If you want something in the same price range that is lighter and more manageable, then bikes like the Bajaj Pulsar NS400Z and the KTM 250 Duke are worth considering. 

Take exhaustive test rides of all the machines you shortlist before you decide. 

In the adventure bike space, you can take a look at the TVS Apache RTX 300, which will be the best all-rounder because of its form factor. If you want a neo-retro bike, you can consider the Honda CB350 models, Triumph Speed T4 and the TVS Ronin. They all are smooth, comfortable, and have reasonable performance, although the Triumph will have a noticeable edge over the other two. 

Both the bikes you have mentioned will fit the bill for your use case. However, both the Triumph Scrambler 400 X and the TVS Apache RTX 300 have tall seat heights (830mm or more), and for a new rider of your stature, they could feel like a little too much, especially at slow speeds and during off-roading. We would strongly recommend a test ride of both before you decide to go ahead with your purchase. 

If these two prove to be too tall for you, something more street-biased (and crucially, lower) like the Triumph Speed 400 or Apache RTR 310 from these respective brands would be a good fit. 

Since you are a beginner, we'd suggest that you start with something a little less powerful and easier to manage. As you've mentioned that you have an interest in mild off-road riding, the Hero Xpulse 210 would be a great place to start. It is a fun bike to ride, very comfortable in the city, and it will be a good motorcycle for you to hone your off-road skills on. Once you've gained some confidence, you can look at bigger ADV motorcycles. But if your heart is set on one of the above two bikes that you mentioned, we'd recommend you try out the Apache RTX 300.