MySql: is it possible to 'SUM IF' or to 'COUNT IF'?

You can use a CASE statement:

SELECT count(id), 
    SUM(hour) as totHour, 
    SUM(case when kind = 1 then 1 else 0 end) as countKindOne

you want something like:

SELECT count(id), SUM(hour) as totHour, SUM(kind=1) as countKindOne;

Note that your second example was close, but the IF() function always takes three arguments, so it would have had to be COUNT(IF(kind=1,1,NULL)). I prefer the SUM() syntax shown above because it's concise.