I got my first bar bag back in the 70's, hung off a wire frame with bungees to the front axle - worked great, easy to instal/remove the only issue was the bag itself was pretty horrible.
A couple of decades later i got my first 7 litre Ortlieb (i still have it, a MKII), held its shape, the mount allowed quick removal and it was/is waterproof! I did try one of their small 2 litre flap top bags - didn't work for me, not big enough! I then bought a 7 lite MKIV as the MKII was looking a bit tired and i'm looking at that as i type this - still looking good after 10 years.
I do use a camera insert to organise the contents, travel docs go underneath, wallet, phone, snacks, batteries etc in the main body, post cards/fliers between insert and rear wall of bag. On tour i use the latest 'clear' rubber map case which takes most maps ok although an untrimmed OS is a bit tight. My bags have the 'bedroll' straps but tbh i don't use them these days apart from for carrying a jacket
off the bike.
I've played around with various bracket options, i hate the locking ones, heavy and whats the point when you want to take the bag off if you leave the bike anyway? so i use the basic Klickfix. I used to use an extension block so i could use bar top levers but i don't use that now as i can actually manage without the extra space.
Whilst if i was looking for new i'd still head for Ortlieb, i don't find the newer bags to be as user friendly but maybe thats just me used to my old skool kit.
As regards aero dynamics, a bar bag actually improves things as it hides a lot of the cables and other mess at the front, more like a useful fairing!
Lighting and barbags has always been a crash, but its not insurmountable and can be better or worse depending on your particular bike and bar set up.