Depend your socket load. IF its in dependent get the higher power like 2400 watt or higher, boiling sure faster. If you socket are shared with fridge or other appliances get lower load.

For me, I use gas to boil, is cheaper

Yes if the socket are loop to appliances like Fridge, or oven.

If all using the same copper wire to the fuse (same MCB), that mean is looping. Same row of powerpoint usually are loop. Not many will have direct. Some but I seldom see now uses Ring circuit.

No need lah, kettle only run 10-15mins a day. If using oven don't use kettle at the same line. Else my risk tripping, worse wires burned.

Well, there are some shared, and owner don't know about it.

if all pull separate line , then i need a lot of MCB....