I'd definitely get the YTFK GTR it will give you that really tight MTL you are looking for. I use mine with only half of the smallest air hole open. It's as tight as a ducks arse. Fantastic atty, worth the extra money over any of the cheap versions.
In my opinion the GT4S is not for MTL. Even closed right down mine just doesn't feel right. It's a great atty for DTL. One of the best and straight forward rta's I've ever owned.
I've only got these two rta's in the last few months but wish I'd gotten them sooner.
Only giving my opinion here as, like you, I love really tight MTL and have never found anything as good as that GTR. The most pleasant drip tip I've ever used as well! 👍