A useful inflection is the "minimum size for max throughput" at 214GiB. That same disk would also offers 38 minutes at the maximum throughput at 3000PIOPs. After that, performance will drop to about a fifth: that's the baseline for a 214GiB disk. Another important thing to consider that large contiguous reads and writes on EBS are up to 256KiB per IOP: most bulk transfers take up far fewer IOPS than people normally calculate.
For most workloads, Burst Is Good: for a fixed amount of money, you'll be able to obtain meaningfully better responsiveness in a program. Few workloads are pushing the maximum IOPS all the time. If you need more baseline IOPS you can make gp2 disks bigger or add more disk, depending on whether you find bandwidth has been saturated or not.