"How much ARR and how many accounts should a #CSM own?"
Depending on which blog post you read, you may be tricked into believing there's a true industry standard around this.
I have found that:
1) the definition of a CSM role is highly variable from company to company
2) the requirements of a CSM vary by the type of customer, i.e. small business vs. enterprise and everywhere in between
3) stage and maturity of the team are a factor
All of this makes me question whether there can be a true industry benchmark at this point.
To answer this question for your company, try the following:
1) Segment customers by size and growth potential
2) Determine tasks necessary for:
a. commercial matters (renewal, upsell, cross sell)
b. business / domain expertise (best practice)
c. technical product expertise
(note: gotta start OUTSIDE-IN here with customer needs)
3) Identify the roles that will own each task
4) Assign resources from the top customer tier, downward
5) Build 1:many programs for business / domain and support needs. These will scale everything.
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There's no one-size-fits all answer, but 150 of the best and brightest minds in #cs will be on a call tomorrow morning, 11:30am EDT to discuss.