I would call the 52 more like a 56 bike. I think your statement about the 54 being a 58 with a low stack is spot on.

Would like to see more bottom bracket drop. Overall, don't think this is a good candidate for modern geometry at all.

I would need a 120 stem on a large. Not what I want on a gravel bike.

love to try this

Endurance?
That geometry looks way too aggressive.
A top tube of 54.4 is paired with a head tube of 130
to get a decent head tube height, you need to go up to nearly 56 TT - far from endurance geo surely?

I would look at stack, not head tube length. 570 definitely seems in the right territory in a M/54ish frame.

Thinking of buying my first Chinese frame, having looked and been interested for the longest time.

Been seriously cycling for over 25 years, had my share of top of the line bikes. I race gravel and mtb, but these days my road bike is only a training vehicle. Gets used most for knocking out intervals during the week, or a long 4+ hour ride on the weekend. Will do a very fast group ride every couple of weeks, but would trade ultimate speed for a little comfort for my road bike. 

Mostly I want a bike that is dependable, durable, and ideally not stiff as a board. I do like to try new bikes every once and awhile, I typically keep a bike for 3-5 years. I am tired of losing thousands when I turn over a bike. But if I got 3-5 years out of a $1000 Chinese frame that has almost zero value at the end, I would still consider that good value.

So my question is, do I sound like a good customer for a Chinese frame? Am I likely to be disappointed in the quality and durability, or the ride quality, especially coming off a bike like the Tarmac SL7?   

If you do think I am a good customer, any recommendations for a specific company or specific frame to use? Would like a least 32 tire clearance. More would be better.