S.T.
i'm glad you're considering a cat, and really glad you're asking questions first. very smart.
i'm going to start with your most concerning question. 'soft adoption' sounds nice but is a terrible idea. do your due diligence first, and when you commit, commit. it's incredibly traumatizing for any animal to start to bond with a family and then get yanked away. and that trauma might well make that cat unadoptable for any subsequent family he might get.
do not go into this thinking it's a test drive. it's unfair to everyone.
DO spend time with each prospective cat and see how it makes you feel. if you're horribly allergic, you'll probably know pretty soon. my husband is mildly allergic to most cats but only has a severe reaction to a few. ditto my daughter-in-law to be (who is a vet tech and has to take meds.) most cats only bother her a little but my siamese sets her off so badly that she increases her meds when she's coming her and (to her great sorrow) she limits her time petting Marley.
yes, you can start allergy shots beforehand.
any cat can be a problem cat but most aren't. don't take the horror stories and run with them. most cats are pretty easy, easier than most other pets.
cats can be conditioned out of certain problem behaviors to some extent, but they're not trainable like dogs are trainable. my cats are good about most things, but will scratch furniture and get on the counters if not checked. we have scratching posts which satisfy the girls, but still have to use a spray bottle (and yelling) with the ancient boy cat. he does like to hook a couch.
that being said, we've had the couch for 20 years and it doesn't look bad. he only does it now and then.
spray bottles are excellent things.
we redirect and/or spray if they get on the counter.
don't leave your chicken on the counter.
they're not like dogs in that you need to find an older one that's litter trained. most cats litter train automatically. you can get a kitten and litter train it in a day. in fact, you might be better off with a kitten, as they won't have any of the psychological trauma of an older cat who has lost its family (possibly through a 'soft adoption.')
most shelters will, hopefully, be upfront about a cat that hates kids. but most don't. the flip side is that you can't be sure that any cat will like YOUR kids. do several visits and have everyone handle and play with the cat BEFORE you adopt.
good luck! i hope you find the right kitty baby to be a family member for years to come.
ETA oh PLEASE don't listen to the advice to declaw. declawing is mutilation. i speak from experience. when i was young i reluctantly agreed to get a cat declawed so i could live with a family member who insisted on it. it went fine, so i thought it was fine and had it done to a cat i acquired several years later. it was NOT fine. and since then there's been a ton of research on how painful and psychologically damaging it is to declaw cats. if your furniture is more important than your pets, don't get pets.
khairete
S.