I never tie braid directly to anything but a swivel. I don't tie fluoro to mono, either, no matter what the knot. Don't worry about swivels. Neither trout (include steelhead), nor salmon care if a swivel is on the line, unless you are using dry flies.
What steelhead will bite is entirely up to them. There is no scientific explanation. They will grab the silliest stuff you ever saw. As a general rule, fresh fish are more aggressive than ones that have been holding in a pool for a few days. Summer-run steelhead are far more aggressive than winter steelhead. Steelhead on the move do not bite, but the moment they stop to rest they are fair game. That is true even for fish that move throughout the same pool. I've watched happen many times in canyon pools.
I've seen steelhead take the tiniest of single eggs in preference to fresh steelhead roe. I've seen them take a tiny, salmon fry pattern and yet refuse a perfectly presented egg pattern. Again, as a general rule, a spinner or spoon is usually more effective than bait for summer-run steelhead early in the season, but will prefer bait later in the fall.
There is too much for just one reply. That is why people write books.