subject to Part-P comment by bd3cc, it can be one of 3 types,
a} main switch +2 RCD's + MCB's with lights & power on each floor on different RCD's.
b} main switch + all RCBO's.
c} main switch + RCD for part board + RCBO's for remaining circuit.
Some circuits don't have to be on RCD's at all, but must be surface run or mechanically protected by earthed metal work, frankly not worth the hassle but if I don't mention it some one will!,
see projects 'PART P' building regs before starting!
seriously, all main switches should be able to carry up to 100A,
as long as your mains fuse is the same as or less than the switch rating no problem.
If the main switch was rated for up to 60A and fuse protecting it was a 100A one then there would be a potential problem of over loading.
Since 100A is max ever supplied to domestic installations by referencing all consumer main isolators, busbars etc at that they are safe.
In fact very few systems ever get anywhere near that load due to diversity, ie never have everything on together,
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