Q: Plan on purchasing a new imac online..some info needed please.

When purchasing new imac on Apple's website. I would like some clarification please.

The  imac I plan on buying is home use for moderate video editing, light room and photo shop.  I am leaning towards the SSD drive over the fusion drive.  Is this the right choice for what I'm using the mac for mainly?  

The specks of what I want to purchase are:

i7, 8 gigs SDRAM (will upgrade later), no option to upgrade video card so standard card i guess.  As for the storage, if I do not chose the 1 TB fusion drive, I have to pay an extra $120 for a 256 GB flash drive.  It may be a novice question but do I understand that correctly that i am paying more for a smaller drive going form the ITB fusion to the 256 GB? 

Thanks for your patience...new technology to me!

Colin