Is it a problem if I keep the 100a breaker since I already bought it?

I am adding none of those things. It's a fairly simple setup when all said and done

How many outlets does the cord have?

From an exterior outlet on your house?

So I have already drilled and wired outlets inside the shed for computer/monitor on one, accessories on another, and a separate circuit for the hanging overhead light

I probably should have posted this in an electrician sub on second thought

Would it be more beneficial to grab a smaller amp box in this case if it means being able to use a more cost friendly wire?

It would need to be about 80-100 feet of wire to account for bends through the conduit and into the attic to tie into the main panel.

There would never be more than 1000 watts of power used at any given time. More like 600W

Right! I did buy a 100amp sub panel that I will hook up once it's time to rock and roll.

Solar is intriguing but south and west of the shed is pretty tree covered. Didn't now if that would put a damper on my generation potential

Here is a imgur link to my shed with relative position to the house.

Electrical box is close by

https://imgur.com/a/lO8bjWR