In order for any serious detrimental health problems to come from keeping birds, you'd have to basically never clean them... but some people with respiratory problems can be sensitive to dander and dust. Same as someone can be sensitive to cats or dogs... or rabbits... or pretty much any animal in the household. Clean, clean, clean. If they are cared for properly, they should have no appreciable smell. Wild bird droppings can be a source of disease though.
Most birds are noisy. Not much way around that. Making noise is all part of being a bird. Generally means they don't make particularly good apartment pets. Of course, some are much louder than others. Finches make little meeping noises, and doves coo, while macaws can deafen you with screeching... but no bird is going to be silent, nor even quiet when you want them to be.
Biting is all about training... but you have to understand that birds stand on their feet, and fly with their wings. Their beak is how they experience the world. So it is completely normal to have a certain amount of attempting to 'taste' things. Keeping nails trimmed will help with scratching, but all birds have grasping claws. The larger the bird, the more damage they can do, obviously.
As for budgies having seizures... never had it happen in years of keeping them. If you're going out of your way to scare them, maybe... or there was some other underlying health problem, but certainly not just because you flicked on a light.
There are many benefits to having your rabbit neutered.
And you should probably give it some serious consideration, but simply saying "inhumane" is a matter of opinion and doesn't really offer any factual information with which to base your decision on.
Sounds to me like you should be looking for pet advice from another friend.