Horizontal vs Vertical syncronization

For complete enumeration (listing) of households, we plan to assign interviews to the supervisor and he/she in turns assigns the interviews to interviewers. Once complete, the supervisor will synchronize with HQ. My concern is, there are enumeration areas with 300, 400 households. Is there any reported major performance issue related to a large number of interviews in the supervisor tablet?

Yes, but rather old one and with a bigger number. See here:

Test your setup thoroughly with a realistic number of assignments/interviews and using your actual devices to get confidence your plan will be feasible.