If your visa transfer application is approved, you can switch say right now... you can switch job on Opt and from 10/1 you will be on H1status with new firm
Second p2. You lose the h1 if you move before oct 1st. May not need 3 paychecks, might be able to make it work after just 1, but depends on the next company’s legal team and their experience/ opinion
Definitely wait until 10/1 for h1b visa to activate and additionally stay until you obtain 3 pay checks ... this is what I would do
If your visa transfer application is approved, you can switch say right now... you can switch job on Opt and from 10/1 you will be on H1status with new firm
Second p2. You lose the h1 if you move before oct 1st. May not need 3 paychecks, might be able to make it work after just 1, but depends on the next company’s legal team and their experience/ opinion