Spent three weekends building my first deck off the upstairs door and it's finally done

I hear you on the initial prep being a killer. I started my own build in May and the hole digging alone felt like a marathon. My main frustration was trying to get the joist hangers aligned perfectly before they were set into the concrete blocks. It was a massive headache trying to get the spacing uniform across the entire span. I ended up using a level on the long side of the beam to check the alignment before setting the first hanger, which saved me from having to readjust several later on.

What helped me was doing the sub-decking with pressure-treated 5/4 lumber before I nailed the top layer down. It gave me more room to maneuver the screws and made the whole thing feel much more solid. If I had gone straight to the final decking, I think I woud have had issues keeping the fasteners flush and tight across the boards. It’s all about those little steps that feel tedious now but make the finished thing feel rock solid.

I agree that the initial framing is the hardest part, but I think people sometimes overlook the connection points to the house itself, expecially when the ledger is involved. Relying only on the joist ties for lateral stability isn't enugh if the post isn't secured properly to the concrete foundation or the main structure. I used several heavy hot dipped galvanized bolts through the posts into the sill plate and then tied those plates to the beams with Simpson hardware. I felt much more secure knowing the load was distributed through multiple points. My biggest change from my first deck was focusing on the fastener selection. I used 3.5 inch carriage bolts for all the main post connections. It gave me a solid feeling of security when I walked across the frame before I even laid any decking. Once the frame is solid, the actual wood and nails don't matter as much as the foundational connections.

Not sure I follow the double decking thing. 5/4 boards are already thin decking, so laying them down as a base layer and then fastening another layer on top just doubles your fastener count and gives water two places to sit instead of one. When I redid my sister's deck I pulled exactly that setup off and the bottom layer was the rotted one, go figure. One layer, proper gaps between the boards so it can drain, done. Curious how you're handling drainage between your two layers, because that's where mine went bad.

Just joined this place after finding it while planning my own small platform build, so still figuring out what all the terms mean. Mine will sit low to the ground so no posts or bracing needed, kind of jealous you went full height honestly.

Since you mentioned the stairs are coming, I'd get them laid out before you touch the last few boards on the edge. I helped my neighbor redo his steps after the deck was finished and getting the first riser height right meant trimming his bottom stringer and redoing the whole layout. Learned that watching him cuss for an afternoon.