3) Should I get the MCBs that say “C60H” changed to be type B (C60HB) so they are all the same, or the reverse, or simply ignore as all is working?
unless you wanted second hand, not advisable, you couldnt get them to be the same if you did want to, them HB aint been made for years and the H even longer, theres new rcbos and mcbs that replaced them , if you ever need any more, but they look totally different.
There are new H ones on ebay, but seem dubious to me considering they aint been made by merlin gerin for ages