On the subject of taking a shower after going to the mikveh, the Rema at the end of simon 201 in Yoreh Deah seems to say the minhag is to prohibit. The Shach there seems to refer to our gemara of yud ches davar. The biur ha Gra is matir saying that the yud ches davar was only an issur for those that ate trumah.
Also in you answer you said that there is a minhag not to shower after the mikveh but that this is unralated to our gemaora. What is the reason for this if not because of the Rema and our sugiah?
Best regards and thanks,
You are correct. The Rema cites a Shitah found in the Mordechai that women should not take showers after going to the Mikvah. Although many Rishonim argue on this (the Mechaber indeed does not mention it, even though he brings the opinion in the Beis Yosef), the Rema says to be Machmir.
I was thinking, at the time, of Tevilas Anashim (men), for which we do not seem to find any Shitah that prohibits showering due to our Gemara.