If your ground isn't too rocky, dig as deep a hole for your 4x4's as you can manage with your post hole digger. A good gravel base at the bottom is always a good idea. If you use concrete, screw some good size screws in the submerged part of your post on all sides and let them project enough to give the concrete something to lock onto (and still fit your post into your hole). You don't have to use concrete. Gradual misalignment can be corrected. Your concrete laden post might be less likely to shift, but it does get misaligned, it will be a lot harder to re-position. I'm just an amateur but I've done a few of these. One thing I would strongly advise is to build your gate in the opening you are going to use it in. The first time I did this I took measurements and made the frame somewhere else, when I tried it I found it to be a poor fit. Instead get a helper and make a level platform at the height above ground you want your gate to be. Cut the parts elsewhere but assemble your frame right in the opening, it worked a lot better for us. A diagonal brace for the door would be much recommended I think.

Leave a clear space just inside the fence and use vines on the fence to provide privacy in that area immediately inside the gate. I looked for pictures of out gate that opens our gate that opens outward (the north alley gate) to try to show what we did. The 'man door' at the back of the garage opens into the alley just inside the gate too so the clear space provides access to that door as well as space for moving the lawn mower or snow blower etc. in/out of the garage through that door. Some pictures: In early May - you can see the basic space a bit better before everything leafs out...: In July - from outside the gate - with clematises in bloom: Looking from the road when the clematises are in bloom: Maybe something like that could work for you...?

If you don’t mind someone looking over the gate into your yard, 5 ft. is good. Personally, I prefer side gates to be the same height as the fence.

I think you just want something simple and clean. A rock/gravel driveway is fine. Line the driveway with a brick trim edge to match the house. Order more gravel. Install a path to the steps. Brick or concrete pads as shown above Paint the gate and stair rail black. Remove the stump and intall a lawn in front. Plant flowering shrubs along the right fence line and ground cover. Install a 3 or 4 foot high fence at the rear edge of the lawn as proposed but in modern materials. Leave a few feet behind it for access. Put in window boxes but painted black I think if you do these things and add more accent plants and rock, bark, gravel, and grass areas to fill in bare dirt as shown above you'll have a nice look. If it were my house this would be my DIY, otherwise i would hire a landscape architect and contractor and start from scratch. Do you even need a gate?