It's not too bad, but what's the strap like on the front when the bag on the back? Most of these contraptions have a very small bag attached to the strap.
The sling bags I've seen are too big for me. They also have too many pockets and zippers. I recently bought this Stowaway Packable Sling in a different color and pattern from Eddie Bauer and absolutely hated it. It was a good 10L size but the little bag on the strap was too small for much of anything. It was so uncomfortable and impossible to wear whether on the front or the back that I quickly passed it on to family members who might be able to use it.
I looked at similar trendy cross-body front wear options in smaller sizes like this Stowaway Packable Waistpack and realized that it wouldn't be any better than a normal small cross-body purse at 9.8"x6"x4". I'd never wear it as a waist pack. I know this way of wearing bags on the chest is a thing, but it just looks uncomfortable. If it's loose it'd flop against my chest as I walk and if it's tight enough to not flop it'd be hard to get into. Plus, it just looks dorky.
I don’t think the sling bag you linked looks dorky in the picture, but it appears to be almost empty. I think that if it was stuffed and stood out from your chest it would "look not so good." On your back would be fine, but then you'd lose the security benefits. A Goldilocks dilemma.
I stumbled onto a UNIQLO Round Mini Shoulder Bag that's shown as unisex and some pictures show men wearing them. I think it's a bit too feminine, but I'm old. It's better for my anatomy, is soft and comfy, is large enough for my stuff, has a long enough strap to wear as a normal cross-body bag and is very simply designed without the multiple zippered pockets so many people love, but I find useless. I bought it in black and have been using it ever since the day it arrived. For travel I need to add a split key ring or small carabiner to the zipper so I can secure it to the strap where it closes. I've already tested both options and both work. That's the way I secure all my zippers on my bags of any type or size.
I think it's really hard to balance the potential travel need for something secure and something to use as a daypack, so I don't. In fact, I almost never carry a daypack period. I'm more inclined to have a thin, folds into nothing tote in my purse or a pants pocket in case I need to buy something.
Not so efficient, but what I really like is a cotton mesh bag with a long handle that will go over my shoulder. I got my first one in Nürnberg when I lived there and used it till it fell apart. My husband once asked if I was concerned about people seeing what was in the bag. My answer was, "that's the point." They can see my water bottles, bread, cheese and fruit and hopefully not be tempted like they might be by a daypack. In trying to help with your question I was pleased to see that, unlike when I tried to replace the one that retired itself, there are lots of washable, reusable, cotton string bags on the market. Even on Amazon -- Premium Mesh Grocery Bags.