Can anyone with more experience tell me if getting one with 512 SSD is such a bad deal?
It really depends upon your needs, usage and how much stuff (work files, photos, music, movies etc) you like to have at hand without hooking up an external storage drive to view. The only fact is that a 512GB SSD is 1/2 the storage size and will read and write data slower than a 1TB (Or larger) SSD, this may or may not bother you.
My 2019 iMac (bought refurbished from Apple in mid 2020) was a 512GB SSD and I soon found out, as a photographerher, the smaller SSD was a mistake for me. My LR catalog and preview files, which I keep on the internal storage, were about 1/2 that amount alone, the actual photos were stored on external drives. Within 1 year I was looking at getting an external drive with 2TB of storage attached via a TB port to use as my startup drive, using the internal SSD as cache storage. I got an Acasis USB 4 enclosure with a 2TB Samsung 980 NVMe SSD inside. It actually had slightly faster R&W speeds than the iMacs internal storage. It worked beautifully with no issue for 2-1/2 years as my daily startup drive.
Today with my M2 1TB 64GB Mac Studio Max I use the same style USB4 enclosure with a 4TB WD Black 850x internal NVMe as my startup drive (My old one is now 4TB as well and my system backup drive). But I am eyeing 8TB NVMe's down the line, which is possible with an external startup drive of this type. A simple 5 minute swap of the NVMe and my "internal" storage doubles in size again.