MC Load Resistance

You have to try it. There is no Standard (unfortunately). The result will be different from Manufacturer to Manufacturer. Phonstage A with 100ohm will not sound identical to Phonostage B with 100ohm...There are a few MC Phonostages out there which have excellent results- Speed, airy high frequency Aera, headroom, deep soundstage, holographic Body - with 47kΩ (Stan Klyne, CTC, Vendetta...) but most will sound thin and lifeless at that Setting. Depends on Design.

That reminds me, when someone listens to his System with a dull cable and asks for something better, that there will be an advice from a friendly "supporter":
"Buddy, turn the volume up"
and the answer will be:
"Great idea. Thank you"
Having no idea isn't the solution

It is a pity, that common Phono knowledge gets buried. Of course the user will find THE exception (SUT or high gain Phono) but may I add something important:
I listened to transformers from horrible-excellent, but honestly, horrible was majority. Colored, wrong in reproduction, channel separation and so on... I did that for 3 years with various units (EAR, Kondo, endless cheaper units) and at the end of the road I use now a top unit with 1.rate studio specs. No Hype, no miracles, just measured - and compared - datas.
And before I did that, I wasn't really mad for them.
Most manufacturers have no idea about the sense behind, they offer it - more or less - to make some money, top trannies are ALWAYS expensive, there is no way out and we know from former discussions, "expensive" is the most hated word in High End
(High End but lowest price, funny eh?)
But honestly, before some readers will say: "Great" after reading that and think, that is the - cheap - solution for everything: no, it's not.
It is just one more piece in the analog puzzle.