That fucker on the right is called a "house centipede" and they take years to get to that pictured size. It's a really terrible experience to be using the bathroom and glancing over at the wall and seeing a 2-3" centipede skittering around. They're not very fast, so they're easy enough to kill, but ugh.
I'd rather deal with a brown bear than most of what Australia has to offer and a grizzly more than some of what Australia has to offer. Polar bears are S tier nope but they're far. Bears aren't even the scariest animals in North America, fucking moose are.
House centipedes are little assholes though, they'll crawl up to you while you're sleeping and bite you a bunch to see if anything happens, then wander off, leaving a string of painful itchy welts.
That's obviously not as dangerous as the average Australian spider, but I have to assume none of those spiders are quite so eager, because otherwise the island would be uninhabitable.
Bad news: spiders and centipedes that live in your house are the latest of generations that have only ever lived in your house. Putting them outside is basically killing them
This is only sorta-kinda true. Depending on your house and the species in question, a lot of spiders and insects you might find in it have just come in from the outside, making their way under door jams or all sorts of not completely sealed cracks and crevices. I often (relatively speaking) capture and toss out wetas in my place that I know just squeezed in from outside. It also doesn't really matter how many generations they've been there as long as it hasn't been so many that they've actually evolved to habitate in your house specifically. What matters in that case is the individual which may have been set up in such a way in your house that yeah, chucking it outside will be a death sentence. But that's really variable depending on the species in question, the conditions outside, where you end up putting it outside (example: out in the open where it will immediately get got by a predator, or in the kind of underbrush it's naturally suited for anyway), and all sorts of other things.