Regarding a job offer and conflicts in CoE with other potential offers in Eikawa work.

I just received a job offer from PKC and have 5 days to answer back.

I will be attending an in-person interview session with ECC in 4 days, and they are currently my first choice.

I want to ask whether there will be issues if I accept PKC's offer now, regarding CoE/visa applications. I'd be projected to leave in November, meaning my application must be done asap. I believe ECC's process would take about a week for an answer after the interviews, meaning it would take around 2 weeks from now before I hear back. However, the start date would be in January. If ECC does accept me, will there be troubles if they go to start my visa applications?

For both places, I requested to be placed around Tokyo & Saitama (1st choice), and Fukuoka (2nd).

I'd like to have some extra advice, should I wait a few more days to answer PKC, and hope the paperwork is not submitted before I get an answer from ECC? Should I tell PKC/ECC about my predicament?

Thank you in advance.