I'm looking for a little feedback on using Squarespace to do commerce

Hello!

We're dipping our toes in the water of selling some merch and I'm running into some kinda brain melting, illogical choices made by the SS dev team and was wondering if anyone had any "workarounds" for a few things. 

What we're mostly struggling with is designating shipping. It seems like it would be standard function to just calculate shipping, but that is locked behind the BIG commerce plan (which is fine) but there doesn't seem to be a way to assign different shipping costs to different items. I asked SS about this and their answer was to add several options and if the customer picked one that didn't cover the shipping costs then just cancel the order (lol). 

If anyone could provide me with better info than is found in the help files, it would be greatly appreciated. I have secondary concerns about integrations/payment processors but the shipping thing is the big hurdle for now.