I think it depends on lots of different factors besides just your capacity: like your goals & priorities (getting more traffic / leads / paying customers; what’s the optimal LTV:CAC for you), your industry, your competitors and their SEO strategies & results etc.

But these things aside, I’d say it makes sense to approach this in a lean manner: start with just 1 cluster (if you feel the cluster strategy is going to work in your case) and 4 long-form articles a month. If you start seeing some decent results over time, then you can dedicate more resources to this.