Is it sensible not to conclude Kfw financing with the main financing bank?

I have a theory that I would like to get off my chest.
Starting point:
House (purchase) + additional costs + modernization = 270k EUR
Equity 60k EUR
Remaining 210k EUR to finance.

Now the KFW does not mind being in second place in the land register.
So if I conclude the KFW loan beforehand, only 210k EUR - 75k EUR = 135k EUR remains for the "main" bank.
135k EUR with 60k EUR equity coverage is almost 45%.
With 210k EUR and 60k EUR it would only be just under 30%.

A higher coverage usually results in a better interest rate.

Question: Does it make sense to conclude the KfW loan independently of the mainly financing bank?
Does the bank already take that into account and calculate with 135k EUR anyway?
Is the bank not interested in my theory at all and do they calculate with 210k EUR despite KfW?
Or does the bank possibly calculate 270k EUR against 60k EUR and only grant me a coverage of 22%?

As far as I know, you have to conclude the KfW contract through a bank anyway. And the loan-to-value ratio results from the total loan amount.

Doesn't make much difference since it goes through the bank. You should just see if you can get a particularly energy-efficient house - then you can later get a repayment grant.

I was at our bank yesterday and discussed it. It is possible in the way I have thought about it. I have to get the KfW loan through the investment bank beforehand and then only have the remaining amount open at the house bank. The equity coverage is then naturally significantly higher, and so I get the top interest rate from the house bank.

This only works because the KfW is listed second in the land register and is therefore not of interest to the bank. I don't know if every bank tolerates this - after all, the bank loses the interest from the higher interest rate.

Hello,

...It is possible as I have thought it through. I have to get the KfW loan through the investment bank first and then only the remaining amount is outstanding with the house bank. The equity coverage is then naturally much higher and this way I get the top interest rate from the house bank.

A peculiarity/fable like no other. ;) I would like to see the "top interest rate" ;)
If KfW is registered first in the land register, since this loan is to be paid out first, it naturally holds the first ranking. If the "allegedly" senior loan comes second, a subordination agreement for the KfW loan is required! Moreover, a KfW loan can only be obtained through a regular commercial bank, never directly! A processing fee is required for this "service". The total loan-to-value ratio and the equity ratio result from both loans, as well as the total resulting debt service and the corresponding remaining creditworthiness!

Best regards.

You apply for the KfW through the investment bank. You can inform them that the house bank should be in first place with the amount X. I only pass on what my financer tells me - if they are trying to pull a fast one on me, I am of course happy to be educated beforehand. However, I can understand this approach. Especially since I came up with the idea before the conversation with the financer :)

The "Spitzenzins" is 3.0x. However, "Spitzenzins" is meant to indicate that I have to pay a higher rate with poorer equity coverage.