Buying a nee build with no realtor

My husband and I made a mistake to go see new builds without realtor as some of the builders are offering 3.75% - 3.99% fixed rate for 30 years mortgage so we figured out why not drive out there to see what the area looks like. We ended up liking one of their floor plans and actually thinking about pulling the trigger. I know the dual agen at the office will help us guide through the process but we are think about asking for more incentives like cover 100% closing cost or upgraded walls and backyard. They told us we could try to write that in the offer and send it to them. Are we unreasonable to ask for free upgrades since we probably won’t lower the principal price? Should we apply for pre approval through their lender first and then send them the offer letter email again asking for some free upgrades? Any recommendations would be very appreciated!

We actually sent them the offer asking to lower the price to $415,000 (they are asking $430,000) and they declined the offer.