What garden fence height would you recommend?

So with us it's like this, the neighbors don't want a fence, but my wife does. And especially because of privacy. We also have a dog who unfortunately doesn't obey well, so with open overall property conditions he would probably just run off sometimes (out of curiosity, not because he doesn't feel comfortable with us). We make at least 1.50m to the neighbors and 1.80m to the street. For privacy, specific zones (terrace, garden seating area) are equipped with higher privacy (planted long-term). Plants along the fence are also planned. There are dogs that can easily overcome 2m with just a little training. They don't jump over you but rather "climb" over. There's a clip on the internet of training with Malinois who climb 2-3m trees and then jump another 2m from there. But don't worry, Labradors are rather lazy. I think 1.5m would actually be enough, even if he got over, he probably wouldn't want to go over in 99% of cases. But privacy only really starts at 1.8m. In the USA (in urban areas where not everyone has a few hectares) it is totally common to build "prison yards." You then decorate them with plants, fun shelves, and ornaments. You can really watch the shows on HGTV for inspiration.

"Flowers" is quite a broad field. Mullein can grow over 2m tall, and if planted densely enough, it already provides good visual screening.

Yes, but they only reach that height in June/July. That is the actual problem with all flowers—they are still small in spring when you have cut off all the dead wood from the previous year.

I would recommend a loose hedge made from various shrubs. Photinia, for example, is great. Then you also have green in winter. And you can trim everything to the desired height or let it grow back again.
And I would never completely surround a terrace. Border towards the neighbor, but then keep it open to the garden. And put the hedge along the garden fence. It feels much more open, more spacious.

What does the insurance say about fence height and dog? We once had such a case. I would go straight to two meters. But no ugly privacy strips. Better to use ivy lattice, which is also dense, green, and low-maintenance. Unfortunately, also more expensive.

Unfortunately also more expensive.

… And very, very poisonous to dogs!

… And very, very toxic for dogs!

But they know that and don’t go near it.