How to use to_jsonb as row_to_jsonb? Where the details about "how much"?

You can just use to_jsonb() instead of row_to_json(), example:

with the_table(a, b, c) as (
    select 1, 'alfa', '2016-01-01'::date
)
select to_jsonb(t), row_to_json(t)
from the_table t;

                 to_jsonb                 |             row_to_json             
------------------------------------------+-------------------------------------
 {"a": 1, "b": "alfa", "c": "2016-01-01"} | {"a":1,"b":"alfa","c":"2016-01-01"}
(1 row) 

The first has a wider application than the other because of the type of arguments (anyelement versus record). For example, you can convert a Postgres array to json array using to_jsonb(), that cannot be done with row_to_json():

select to_jsonb(array['a', 'b', 'c']);

    to_jsonb     
-----------------
 ["a", "b", "c"]
(1 row)

In case of the use of two arguments in row_to_json() you should additionally use jsonb_pretty():

with the_table(a, b, c) as (
    select 1, 'alfa', '2016-01-01'::date
)
select jsonb_pretty(to_jsonb(t)), row_to_json(t, true)
from the_table t;

     jsonb_pretty      |    row_to_json     
-----------------------+--------------------
 {                    +| {"a":1,           +
     "a": 1,          +|  "b":"alfa",      +
     "b": "alfa",     +|  "c":"2016-01-01"}
     "c": "2016-01-01"+| 
 }                     | 
(1 row) 

you can cast json to jsonb row_to_json(...)::jsonb, not ideal but often does the trick

You can use to_jsonb as a drop-in replacement for row_to_json.

SELECT to_jsonb(rows) FROM (SELECT * FROM table) rows;