I am apparently a gear whore, I have managed to collect up several types of vests and pouches etc. My favorite is the chest rig, its not bulky, at least up high, easy to grab and go and its universal so it takes AK and AR mags, even FAL mags in single. I also have a couple surplus brown USMC Molle vests that I have tailored to my specific use without all the extra pouches etc I don't use. Mostly mag double pouches, a dump pouch and a SAW pouch for snacks.

Both are not worse than putting on a jacket.
Not that its relevant to what you want, but I picked up a Brit arid DPM "expedition" vest that is interesting, an interior pistol holster and double mag pouch, multiple large pouches externally, along with 2 double mag rifle mag pouches, it would be my go to vest if I had to be out and about for an extended period. But its a bulky full on vest.
But for the grab it and go, I have made a bandoleer type thing using a triple double molly mag pouch, with a SAW pouch and a small multi pocket admin utility bag attached to the front, I used a snap hook rifle sling for strap. Its loaded with mags with specific ammo in each pouch, and cleaning kit and oil in the utility bag. Throw over the shoulder and you're out the door and its easy to get off quickly. The down side is its stability and balance, not real friendly to a lot of movement, any running etc you are going to use a hand to keep it in place.