Three suggestions:

1. Go to the store, sit in the chair, and buy the one that feels comfy but won' break your budget. Other than that don't worry about it.

2. From my past experience in the web 1.0 era I've found that startups that focus on furniture over their own product don't do well in the long run.

3. The real thing you want is a HUGE whiteboard.

I am either sitting on the couch with my laptop on my knees or at a standing desk.

Some leather desk chair (don't even know the brand).

Herman Miller Embody.

I stand!

juststand.org