2. Excavator, Most people that use UL excavators do so for speed. I certainly do, especially on larger claims
4. I can see no reason why, let alone mechanics for doing it, for MA to take MU and tax on finders and amps into account. They would need to track every transaction you made, on AH, in a shop or P2P sales, calc the MU, and then apply it IF and WHEN you use it, part use it etc Also ofc track you to see if you simply trade it to a third party.
MU is therefore wholly your problem as a miner. You have to ensure you buy your kit at a reasonable MU, and mine things that will return that MU.
5. HOF/ATH in other professions should according to MA have no effect, they have repeatedly said the loot pools for the 3 professions are separate.
8. Amps and to some extent Finders are according to most miners I chat to and also in my own experience a matter of personal preference and balamce.
To a large extent it will depend on what you are mining and where, as to which finder is best suited (think depth etc) As for amps 2 people with near identical set ups may choose different amps, and both claim it works best for them. I personally hate D-Class yet many love them. Also remember some resources are almost never found amped.
So as Rufen said, get out there and mine, keep your own records and work out which set up works best for YOU., and in which situations. Re-assess as your skills grow. Most miners have 2 or 3 set ups on the go.
If there was an ideal set up, for all skill levels, locations, etc then we would all use it, the MU would go through the roof, and the rest of us could pack up our gear and go home