Of all the bikes you have shortlisted, the Triumph Speed 400 and Royal Enfield Guerrilla 450 will be the most usable without sacrificing performance due to their upright ergonomics and powerful 40hp engines.
The KTM RC 390 will feel the most at home on winding roads, but inside the city, it won’t be the most user-friendly with its canted forward riding position and peaky engine. Speaking of committed ergonomics, the Triumph Thruxton 400 is by far the most uncomfortable machine here. If you plan to use it daily, you will need to put up with a seriously focused riding position.
Coming to the two 310s, the TVS Apache RR 310 has been kept fresh with small updates every year, while the BMW G 310 RR has stayed pretty much the same since it came out. The TVS is also more affordable and packs in more power, features and better componentry, but if you value the BMW badge, then the G 310 RR is the most affordable way into BMW ownership.
We’d also recommend taking a look at the KTM 390 Duke because it is a bike you can commute on during the week and have fun on during the weekend.
A test ride should help you decide which is the best bike for you.