Bespoke size 7ft x 4ft that is firm but soft at the same time?

7ft by 4ft bed and Ryon mattress with fitted with allot of pocket's springs to make firm BUT ALSO SOFT AT THE SAME TIME will i have to order something like this
i mean allot as well could you get back to me on this price's per spring or if you have one that size in stock then get straight back to me on this matter