I use a chest pack or fanny pack(across my chest) pretty often because I have 12 screws in my neck from Neck Micro Fracture surgery and carrying almost any handgun on my hip is not comfortable. I am learning that carrying my Glock 19 Gen 5 in Appendix carry in a Bravo Concealment inside the pants holster is pretty comfortable.
I like riding my electric bicycle and a chest pack or fanny pack across my chest covered by a reflective vest allows me to carry pretty much whichever firearm I'm carrying that day. I also carry pepper spray for the aggressive stray dogs I sometimes encounter on rural rides.
There is no argument that drawing from a fanny pack or chest pack is slower than drawing from the hip. I'm in a different boat than most concealed handgun carriers as my 2nd option(if verbal de-escalation does not work) is a knife. I've been involved in martial arts training especially the Filipino Martial Arts for over 35 years.
I can draw a knife faster and quieter than most people can deploy their firearm. I have martial arts students who are Law Enforcement officers from different levels, local, state, and federal. We have done scenario training with knives and unloaded firearms.
I'm pretty familiar with the most common ways concealed handgun people carry. What some concealed handgun carriers don't realize is that a knife can be deployed so quickly from more parts in the body that a handgun can. For example a small neck knife can be used to cut your gun hand and allow the knife carrier to then cut the Carotid, Brachial and other vital points.
We train in Escrima to "De-fang the snake" attack the weapon which on my most people is their hands.
The point I'm trying to make is that carrying a firearm in a chest pack or fanny pack is slower but that can be offset by other factors. In my case it's a knife that's always on me that I can deploy with either hand, even if I'm on the ground. Additionally I also have empty hand techniques to compliment the knife and firearm techniques.
Over the years I've known firearm people who think their firearm is the only self-defense tool they need. My experience as a martial arts instructor, bouncer, bodyguard, mental health associate, shows different.
Your firearm should be the last resort, so spend equal time on verbal judo, basic empty hand techniques that help you create distance to escape or God forbid give you space to safely and accurately use your firearm.
One final note, I also train in firearm retention, which is another of the other little things firearm people need to be aware of and consider as part of their training.
Some firearm people are quick to criticize the firearm and type of carry of others, while they have big holes in their personal self-defense plan.
I train daily practicing direct and indirect applications to self-defense. Verbal de-escalation(Sorry sir, I apologize, etc, etc), footwork, awareness, being able to draw my firearm without looking at the firearm, pushing a hand that grabbed me, avoiding being taken to the ground (sometimes called "Sprawling" in Brazilian JuJitsu.).etc, etc.