I can't help you with that much of this, as a lot of it is related to electircals (ground etc which any electrician should be able to help you with) but:
for smaller cases such as 7u and 4u - hinton style busbars are almost definitely massive over kill - for a 60u 168hp + wide case then they are probably a good idea...
for eurorack power cables - which won't work with hinton style busbars anyway (you need all custom cables for this) they're alnost definitely just standard ribbon cable and 10 and 16 pin idc connectors which can be bought from most electrical suppliers - I'm sure there's one in Sweden, but otherwise Tayda, Mouser, RME, Reichelt etc carry them
if you already have long cables that you want to make significantly shorter - then it's easier to just cut them and add the appropriate header
you can either get a specialized crimper (I got one for 8€ from Reichelt) or use a vice or a heavy book - there's a video on YouTube using a bible for example
"some of the best base-level info to remember can be found in Jim's sigfile" @Lugia
Utility modules are the dull polish that makes the shiny modules actually shine!!!
sound sources < sound modifiers < modulation sources < utilities