IRC section 311.7.11 have a read through that.

Brad nails are a monstorous no in this construction. If it’s all of solid wood lean toward white oak or at the least Douglas fir. Through bolt the treads by extending them back to overlap the stringers OR create triangle wedges that are bolted to stringers then downward fasten treads through and plug holes.

There are other suggestions on cutting I’d recommend the table saw undercut and then Japanese hand saw or standard very sharp handsaw to finish. Cutting all this is the easy part the assembly is what will take a long time.