First time deck builder questions

Opinions and approaches will differ because there are cheap-good ways and expensive-good ways to achieve things.

For instance, I've used double-threaded stainless Spax screws for my hardwood decking. I could have probably used partially threaded screws instead, particularly since I had to pre-drill the decking boards to stop the hardwood from splitting. But the double threads give a bit more security and possibly prevent water ingress through the hole into the joist below. Is it worth it? Don't know. I also could have used cheaper screws - even the Wirox-coated Spax screws are significantly cheaper than stainless. I've previously used thinner, cheaper green deck screws from the builders providers with treated softwood decking and they lasted longer than the decking.

I wouldn't be generally concerned about fastener corrosion if you're using stuff designed for outdoor use.

A big factor is keeping structural timber out of wet ground contact. You can use adjustable plastic risers, DPC strips, well-drained angular gravel. Just decide on you approach based on the characteristics of your site and execute it well.

Joist hangers aren't strictly necessary - you could probably get away with toe nailing. But I've used Simpsons hangers and they're great. Whatever you pick make sure they're the correct dimension - don't base it on nominal timber dimensions - measure the timber you're buying and get the exact fit.

Treating cut ends is a good idea, most important for exposed vertical ends that will have water pooling on or under them, although you should try to avoid that wherever possible. I've use Protim before.

Joist tape is a good idea too but don't go overboard. I've seen some mad priced stuff used by sponsored Youtubers before. A roll of DPC will go a long way, you're just looking to shed the water off.