Is there a good source that someone can point me to that will explain or rank
the various ways that excel can work with data according to how efficient the
code will work?

I.E. how does =Index(cellarray,match("lookupval",cellarray,0),H1 ) compare to
Copying the data for cellarray into a sorted cellrange then doing a vlookup.

Is there an add-in, tool, trick etc. that will observe workbook
recalculations and report on which sets of formula are the resource hogs?

--
Regards,
John