How do i install modern vinyl siding on a garage near no overhang on the roofline? ...

Should I use PAR30 or PAR38 lights for...
Answers:    After you put the siding on, put a new drip brim on. Slide the new drip rim under the shingles as far as you can. That will furnish you a watertight "cover" and prevent water from running down the siding.

If you cannot do that, and you choose to do it the first persons process, make sure you put a correct solid bead of caulk behind the J molding.
When I try to wishy-washy a fire contained...
You requirement only more or less 3/4 inch (the J-channel thickness) of over hang. Most gable ends enjoy at least a fascia board that give you this much overhang. If this is a residing, the old siding wants to be removed to give you rather overhang.