It is not totally necessary, years ago it was rare to have third axis regulation and we killed animals, but it is advisable for those shots out of the normal that may well happen
I have a 3-pin hogg-it, bomb proof, third axis regulation and I bought it used very cheap
I guess the grinder is perfect to start with, I prefer hogg-it or hunter
I only use a hunting bow, I have another one for the tree stand, but I don't usually use it
with a single bow it is easier to have confidence in the shot at that critical moment, since you know it well, just my opinion