There is no increased risk of tip scar tissue after an Asian rhinoplasty; this has never been my experience. The contour if the tip cartilages should be changed and grafts placed to support the narrower, better defined tip achieved during surgery.
Your concern is valid given your history of keloid scarring. There may be more collagen deposition in the tip following asian rhinoplasty due to your history. Typically, scarring is not a concern in asian rhinoplasty. Rather, due to the thickness of the skin, swelling takes longer to resolve and healing time is longer. To improve definition in the tip we will use cartilage grafts to "tent" the cartilage structure into the overlying skin. Other techniques, like thinning the fat off the undersurface of the nasal skin during surgery can help as well. Steroid injections can be used as the last resort.
The most important thing is to find someone who is experienced with asian rhinoplasty to help you achieve the results you seek. Please consult with a board certified specialist who can assist you with achieving the results you desire. 3-dimensional computer imaging can also help you visualize what you may look like afterwards.
Asian rhinoplasty and scar does not make tip bulbous in my 35 year experience of doing theses. The fatty fibrous tissue can be removed to lessen the thickness of the nose, etc. See an experienced rhinoplasty surgeon.
Thank you for the question and the diagram. The issue that you are describing is certainly possible. However, it is generally avoided by thinking the skin of the tip region from the inside during your rhinoplasty. In addition, after the surgery, there is some utility in placement of small steroid injections to the tip skin. Lastly, as shown in the diagram, I will often use a small cap graft to help with tip definition in Asian patients. Best of luck moving forward!
Complications can occur with any procedure but in the hands of an experienced surgeon you should reliably get the desired result