1) US model, guards only rewarded for catching criminals or deporting. Lots of false negatives at no cost to guards so they fuck with you a lot for no apparent reason. Canada somewhat similar.
2) LatAm model, bribes/theft to incentivize the to not burn up time with false negatives, but they sonetimes are rewarded enough for true positives to not just let them go.
3) "Swedish" model. Straight salary and then not give a fuck. Seems everyone gets through with not much thought.
LatAm model seems most practical of what I've seen but I haven't spent much time in Europe or Asia, mostly middle east, the Americas, and southeast asia.
LatAm model where they're too busy robbing people to care about actual threats (who are generally particularly happy to pay them off, including offers of recurring payments) seems like obviously the worst of both worlds. Though frankly my own LatAM border highlights were watching Ecuadorian airport staff meticulously searching the multiple suitcases every local family brought with them from Colombia and then not even bothering with a token gesture at my bag, and having no real issues at land borders despite crossing them with a strikingly different-looking temporary passport. Apparently the Bolivian border guard was enthusiastic enough about his job to give US Americans a lecture on why they had to pay to arrange a visa-on-arrival everyone else got for free
Or even less your first theory about how a bribe based system is necessary for an immigration system to "bring in good productive people" which frankly is a 180 degree pivot from a story about border guards indiscriminately thieving from everyone, as well as obviously falsified by the many countries where border staff neither demand unofficial payment for entry nor routinely assume that anyone who looks a bit funny is an illegal alien or a drugs mule.