Welcome:). We will need more information from you. What brand drive/firmware? What media MID type? From the final burn window, you can choose burn speed from the drop-down menu after the blank disc is inserted and identified by nero...is this where you are saying nero 'blanks the burn speed option'?
Another option to try is to UNcheck the nero default burn option in DVDShrink and just burn to HDD folder, THEN open nero and choose a burn speed in the final burn window as described above.