Not expert, but as enthusiast I have read some about this (for https://tablam.org).

KV is truly ill-suited for this.

Is very easy to see if you put the data layout:

    --data
    pk  city    country
    1   miami   USA
    2   bogota  Colombia

    --As Kv (naive):

    pk1:    1
    pk2:    2
    city1:  miami
    city2:  bogota

    --As btree, with "value" being N (as you say):

    Key    Value

    1      1    miami   USA
    2      2    bogota  Colombia

    --As paged btree

    Page1
        Low: 1 High:2   
            //think this is a block
            1   miami   USA
            2   bogota  Colombia

    --As columnar:

    pk:     1       2
    city:   miami   bogota

    --As PAX (hybrid columnar/row)

    Page1
        Low: 1 High:2   
            //think this is a block
            pk:     1       2
            city:   miami   bogota