So first I will say that it entirely depends upon what you mean by high and low in your frame of reference.
The next question would be what is your goal from seeking this WOE(way of eating).
High proteins are not really the issue as much the energy source you choose which is either fat or carbs.
For instance:
If you are medium to low carb and high protein and low fat you may benefit but the key to a diet like that is insulin management. The liver will produce glucose if your blood glucose goes low via GNG. If you add exogenous glucose in the form of carbs you don’t need the liver and it will shut down the process and insulin will rise trying to force the glucose to storage if the level gets too high. Any extra fats in the form of triglycerides would be stored as well. The whole problem with that scenario is that you really have to manage intake of carbs to not become insulin resistant. Not ideal but not impossible to live under if you monitor things.
I would be concerned long term about kidney issues and IR but probably not as bad as the Standard American Diet of high fat high carbs medium protein. GNG is not an efficient process and I would tend think over time that you would become gouty.
In your way of eating, the one day a week you are spiking your glucose/insulin and when you do that your body tries to store the glucose as fat (LCT) via the liver. Not having extra fats floating around helps this process, but because you may have been using gluconeogenisis (GNG) instead of ketosis, because of your higher proteins you will probably never burn much of that fat off. Its hard to say for certain, some people are sensitive enough that you could be in keto already based on your carb intake level. Until you have that high carb day then you get knocked out. The benefit to ketosis is that you are shutting down the fat storage cycle and turning on the fat burning cycle, This releases ketones as a byproduct which is a also a form of energy that is used by the brain among other cells.
In an ideal setup you either want high carb very low fat, or very low carb and high fat with protein medium to medium low. The fat or the carbs are your energy and such you should not really intermingle them IMHO now that I understand how this energy management works. If I were to choose, for no other reason outstanding I would pick LCHF(keto) every time, because of the insulin spikes and the whole host of issues it causes.
As for your second question, carb loading or carb back loading. The overall 20g macro is designed to be low enough that more or less anyone will not be knocked out of ketosis, some people skirt that macro some people are nowhere near it like me, I am on the order of 55g. If you are actively exercising the loading of carbs at that level will not likely shut down ketosis, Because your body will be using them more or less right of way so the blood glucose level will not rise enough to get a major insulin response other than the ingestion of the carbs itself. Its also possible that someone who has enough protein in there blood stream and starts to exercise may use GNG more than ketosis if they have that available. So in your case having high protein and trying to back load could knock you out if you are even int ketosis. A that level though you are really going to have to experiment and figure it out. Also I will make big note and say once you are fat adapted most all of that it is not an issue unless you really like to do heavy duty lifting. I hope this helps.
But I bet you’ll look at the number and think it’s awfully small. Several people here will tell you that you don’t need as much as you think, and that you’ll still be able to add muscle.