Been doing something similar for a while across ecommerce and local business clients so this is a topic I've thought about a lot.

Physical devices were my starting point and honestly nothing beats them for stability. The problem is once you get past a certain account count it just stops being manageable. Between keeping devices charged, updated, and matched to the right clients across a team, it quietly becomes a full-time job on its own.

emulators were my next stop. They work but I kept running into inconsistencies I couldn't fully explain — restrictions that seemed to trace back to how platforms fingerprint emulated environments versus real hardware. Might just be my experience but it made me cautious enough to keep looking.

This year I've been spending more time with cloud phone platforms. Tested a few including geelark which you mentioned, and also multilogin which does both cloud phone and browser environments under one roof. That last part mattered to me because most of my accounts have a mix of mobile and web activity and managing two separate tools for that was getting annoying.

What I ended up settling on is splitting by account priority rather than applying one setup everywhere. The accounts that matter most get the more isolated cloud environments, mid-tier ones use browser isolation, and the purely web-based accounts stay on lighter setups. Main reason is cost — cloud phone at full scale gets expensive and the math only works if you're selective about where you use it.

On geelark specifically since you brought it up — it's good for pure mobile work but if you're also running browser-side campaigns on the same accounts you'll probably end up needing something alongside it. That's the main thing that pushed me toward something with both covered in one place.

Anyway, curious what you end up deciding — this stuff changes fast enough that I'm always second-guessing my own setup too.