When a breast reduction is performed, the majority of patients in my practice are getting them for physical symptoms and the surgery is covered by insurance if approved. That is the first hurdle. Insurance companies can have very strict criteria for what is considered a reduction. Things that may be considered and documentation requested include photos, height, weight, Body Mass Index (BMI), previous nonsurgical treatment, prior physicians care. That is just the beginning. Then, you must state how much breast tissue will be removed and a weight in grams of breast tissue to be removed must be the goal. That is an important aspect of this surgery and will dictate some of the answers to the other questions you have asked. Especially since implants and reduction would not be O.K. with insurance companies.
You state that you would like a perky D cup from a 34DDD. Unfortunately this is not an exact science. Both reducing to a certain cup size and the bra to fit are variables that are not precise measures but rather general guidelines. Manufacturers of bra vary on similar bra sizes and especially when you go above a D. Some will use DD, E, or F so bra size is at best a guideline.
To answer your question, a reduction in general includes the lift as a part of the surgery. So every woman who has a reduction will get a noticeable improvement in appearance. The fact is that the breast will not keep that initial shape since the thinner skin below the breast will stretch and superior pole fullness (the fullness of breast which is lifted above the nipple) will move down and "bottom out." The key is that if your breast look perfect after the surgery that with time this shape will change time and the breast will appear more bottom heavy.
An implant will help maintain that superior pole fullness as it will not sag with the rest of the breast. The timing of implant placement in a case like yours varies with doctors. Since you would like to keep a relatively large breast, I would expect for some bottoming out. Your plan of reduction first seems reasonable and waiting on any implants would be wise. This is one of the most difficult aspects of breast surgery. How to make something bigger and smaller at the same time. You should be happy with a reduction and time will tell if you desire more. Just my opinion and good luck