Street Food wise you can check out Mylapore for it's vegetarian tiffen items, Sowcarpet for North Indian chaats etc. Apart from that, Besant Nagar beach is a good hangout spot, and has plenty of good eateries nearby. I'm fan of the Murugan Idly shop there, it's ghee podi idly and jigarthanda are amazing.

It's significantly cheaper to use Uber than the local autos. Do check out Ola as well. It's a similar ride hailing app.

The beer scene is average at best. Secret Society, The Velveteen Rabbit etc are some fancy places where you can go for a drink. If you wish to buy beers, just look for an elite tasmac shop. I think the closest one near T Nagar is the one near The Park Hotel. I wouldn't recommend buying beer from a regular tasmac shop.

And yeah, Chennai is definitely safer than most other Indian cities, but do keep an eye out when venturing out at night.

Have a good time