Growth strategies for SaaS companies?

Trying to research business models, KPIs, metrics, and growth strategies for large SaaS companies (e.g Salesforce). When thinking about short and long-term growth strategies for these larger SaaS providers, what do you guys think is optimal? Is it better to focus solely on large enterprise clients and increase bookings / revenue that way? Or should they also pay attention to medium-sized enterprises and try to upsell over time? Are smaller enterprises even worth the sales resources? Mix of everything?

I feel like it's much easier to say that they should target only large enterprise clients, despite limited upsell potential / longer sales cycles / etc., but the easy answer might not always be the easy (or right) solution. Would love some different perspectives on this.