As for who I personally support, Bernie all the way. I don't care if he's old. So what? What, are you worried he dies? If he picks a good VP, we could actually get more than 8 years of that VP if he were to die in office. But he won't, he's healthy. Nothing beats his consistency. He's been on the right side of history for 40+ years, even when it was incredibly unpopular to do so, and even when it sidelined him politically. You can't beat that in authenticity, consistency, and trustworthiness in a politician. Even if you don't agree with absolutely everything he does, you know he'll stick to his principles and that he genuinely wants to do right by all of us.
As for his VP, as of right now, I'd be open to Warren, Yang, and Buttigieg, in that order. Never Gabbard. I'd take Harris or even Gillibrand before Gabbard. I'm no establishment guy, but I'm not that desperate to be anti-establishment that I'd trust Gabbard. Hell I'd take Biden before Gabbard. It won't come to that, of course, as Bernie has plenty of choices. Gillam and Abrams aren't running for president yet, but whether they do or not, they'd make great VPs. Remember, the VP doesn't have to be a presidential candidate. I'd take Nina Turner, Sherrod Brown, Tammy Baldwin, amongst others. If he gets a second term, AOC would just barely be eligible and would instantly be my number one pick for his VP.