Yeah reference is a subtype. Sounds like you've worked it out from there.
For the Selected flow, if you need to have complicated logic, then yes you're going to need to build a flow. That is in the realms of low code in my mind, but is a step up from the catalog builder.
However your best bet to start with is to go with "Step Based Fulfilment" - it's one of the OOTB flow options (I might have the wording wrong). Once you've selected that you can add tasks and approvals with the click of a button via the catalog builder. Once you've selected "Step Based Fulfilment" you'll get other options appear on the screen below that dropdown.
Then if you want to be really clever for your users, you can write your own steps that populate that task dropdown. Recently I've added on that automatically adds a user to an Entra ID group. This now allows my citizen coders to builder software request SRs that automatically add someone to the right group, once the request is approved.
This blog post shows how you set up the step based fulfilment (steps 4, 5 and 6 - ignore the rest I think you've already worked that out):
https://www.servicenow.com/community/developer-articles/set-up-quot-step-based-request-fulfillment-q...
