Contemplating on a trip between Early Sept - Late Sept and Late Sept - Early Oct

Been researching for the past week now and still can't really decide on which one to go for. Time is flexible and assume we have about 10 - 14 days for either trip.

Key Take away from what i've learnt:

Guaranteed: Westfjords + Snaefells

Early Sept Trip:
- Westfjords (3 - 5 days) - 4x4?
- Snaefells (1 - 1.5 days) -> whale watching (not a must but want to see an Orca(unlikely))
- Highlands (4 - 6 Days) - semi-private to private tour?
- Some of south coast + Snorkel at Silfra (Glacier Hike maybe Diamond beach + Lagoon?)

Late Sept Trip:
- Still Westfjords at Sept -> South Coast, no Highlands
- Still diving at silfra and some of golden circle
- More chance at aurora
- Ice caves + Glacier hikes (what we really want, or should we go some other time?)
- Sunset/ sunrises at diamon beach + Lagoon

I love photography hence looking for these times when its mostly sunset/sunrise, but super basic since just using my Samsung phone so would enjoy the trip regardless.

Can someone pull me in either of the direction just to help put my mind at ease and share some experience, can't go wrong with either i guess?