I could use a little advice on what is the best way to start laying an engineered hardwood floor. I've recently purchased a house and while they put new flooring on the first floor and stairs, the upstairs was carpeted. This is a tounge and groove flooring that I will be nailing down.

I have a couple of questions.

What is the best way to start on the second floor? I know the general advice is to find the longest exterior wall and start off it. However, in this case I have 1 strip of flooring around the perimeter of the stairs. Does it make more sense in this case to start my rows against what is already there? If so, any suggestions on where? I have attached a pic of the stairs. Would I just butt up against it and face nail?

I've laid floating floors and handled levelling the slab. How does this work with a nail down floor? I do have a couple of spots where the plywood sheets aren't perfectly flat. I could sand down the ridge. Do people use self leveling compound on the wood floors? If so - how would you nail into that?

Thanks for you suggestions!

Picture can be seen here:
https://imgur.com/a/A9vIjBf

Take the time to make a few measurements and find out where you'll end up - for example, while I prefer to start at any preinstalled nosings so that that is a full board and flush, depending on material width you may end up with an unsightly shorter rip against the wall opposite. In that case, you may not want to start with a full board, but maybe rip off an inch, so on the opposite you are not left with a small piece. Most people do not mind the smaller piece at the wall, as it's often hidden by shoe and baseboard.

For the subfloor, yes you should rent an edger and sand the high spots in the plywood and all the seams, otherwise you'll see the ridges telegraph to the hardwood. You can use self leveller, but not recommended unless you are doing a floating install, or glue down, since you don't want to be nailing though it.

Also, don't face nail that first row if you start at the nosing, use glue and some weights.