Should I get a job in a cold email agency? (Experts and Real Agency Owners are invited for suggestions)

I'm starting out my cold email journey, and I've learnt almost everything from campaign creation to diagnosis. I've also ran campaigns before but at a smaller scale with more personalisation.

I want to know if I should start at an agency for learning from the real operators or just start my own agency.

Working under actual agencies will fasten my learning and help me grab on SOPs quicker.

If yes, how should I find which agencies are hiring for such roles (Eg. Account Managers, Cold Email Experts, etc.) right now?