am i thinking about this wrong, but i thought one could do something like

const subnet = aws.ec2.Subnet.get("some_subnet_name")

to look up an existing subnet or vpc, but apparently i need to also provide the resource id?

The

<resource>.get()

methods always require an ID. There are lookup functions like

aws.ec2.getSubnet()

that take filter arguments - https://www.pulumi.com/docs/reference/pkg/aws/ec2/getsubnet/#using.

so something along the lines of this is in the right direction

const vpcName = "dev";
export const vpc = pulumi.output(aws.ec2.getVpc({filters: [{name: "tag:Name", values: [vpcName]}]}));
export const subnets = pulumi.output(aws.ec2.getSubnetIds({tags: {Environment: "dev1"}, vpcId: vpc.apply(x => x.id)}));

looks roughly correct, yea

does the python api suffer the same promise/output types of complexities?

Same support and functionality there, yes. 😉