Twenty rebuilds CRM around the interaction patterns people already know from modern productivity tools: keyboard navigation, inline editing, flexible record views, and a data model you can extend without a consultant.
HubSpot's free CRM is a genuine product rather than a trial, and that is the strategy: get the contact database in place, then sell the marketing, sales, and service hubs around it.
Salesforce is less a product than a platform with a CRM at the centre. Objects, fields, validation, and automation are all configurable, and an entire consulting industry exists to configure them.