General speaking:
Standard Transactions: All record types available as a 'type' filter on a new Transaction
search. All 'Transactions' have potential GL impact.
Standard Non-Transactions: All other native records. (ie: CRM records [entity, case, project, ...], item records, etc)
Custom Records: Anything created in Customization->List, Records, Fields->Record Types
These will all have a record id prefixed with customrecord_
When in doubt, verify! There are several ways you might do this, but here's a really basic one for debug console or client script usage, gives you the before and after usage after loading the current record:
console.log(nlapiGetContext().getRemainingUsage());
var test = nlapiLoadRecord(nlapiGetRecordType(),nlapiGetRecordId());
console.log(nlapiGetContext().getRemainingUsage());