If a Muslim does a makruh action, like if they trim their beard short (according to the shafi school) is it haram that they enjoy the look of it or if someone copies their sheikh's style of beard (while knowing a longer beard is better and closer to the sunnah). What is the remedy for waswasa on fear of "being pleased with sin" / "approval of sin" or waswasa on"fear of istihlal". Any advice for someone who gets waswasa about intentions and obsessively thinks about permissibility and compulsively researches about matters.
The issues of makrūh (disliked) and mustaḥabb (recommended) are not commandments but things that are on an equal footing with a person’s cultural and personal context, meaning that if they have a reason to do otherwise, this is not a sin. It is left to their own logic and preferences to determine what to do. If these things were meant to be commands and prohibitions, they would have been expressed as such. But they are not.
The solution to your waswasa could be to dedicate yourself to the Quran and its commandments, making it the constitution of your life. As for the makrūh and mustaḥabb things, by considering them equals to your own choices and preferences (rather than considering them orders meant to control you), you can perhaps convince yourself not to be bothered by them. Of course there are different levels of makrūh, so I am not recommending just ignoring them all.
You should study each issue and decide what you should do about it. If you can accomplish a Quranic character in yourself then perhaps you will feel confident in your Islamic identity without being bothered by such issues as beards.
At least, that is my approach. I am dedicated to following every letter of the Quran and every proven command and prohibition of the Prophet . This is the constitution of my Islam and enables me to feel fully “Islamic” in my identity despite the fact that I do not have a long beard.
If the Prophet was among us, I would have done whatever he commanded. But since I consider him a gentle and friendly mentor, when he makes a recommendation (rather than command), I believe he would respect my own choices in the matter.