Without a visual clue as to your appearance any real assessment of your appearance is impossible and all answers should be regarded as general in nature.
"I like the look of Breast implants" - A well-chosen implant and executed breast augmentation does NOT look "done". As a matter of fact, few can tell if such a person had a breast augmentation. You appear to like the artificial, round encapsulated breast look which most plastic surgeons prefer to avoid. Such results are not hard to produce - all one has to do is to do several things we should NOT be doing.
"I...appreciate how perky the breasts are ( I would aim for a large D or DD)". - A perky breast is a result of youth, continued breast support and perfect coordination between the location of the nipple complex, breast surface area and breast fill. Attempting to reach "perkiness" nirvana by ever increasing breast implant volumes always fails. Skin being stretchable, will always give under the weight and all such breasts will rapidly sag,
"I have heard that if a woman has stretch marks on her breasts and gets a larger implant, the stretch marks will be less visible" - Totally false. Stretch marks are more aptly called stretch cracks. They are full thickness, permanent cracks in the skin caused by rapid stretching which fill with scar tissue. As the skin is FURTHER stretched with ever larger implants the stretch marks do not become narrower - they become wider and more prominent. Larger implants will NOT improve stretch marks and may make them much worse.
Dr. P. Aldea