I'm a regular LFS builder. I like the idea that everything is up to date, as fast as it can be and working as I expected etc.

This is the way how I understand the things:
If I compile a package, then command ./configure checks, what programs and libraries in my system presents and what not, then it makes Makefile(s). Some of the things are needed and some of them not that important.

Ok. Here is the question:
Will the compiled program be faster, more stable of some way better, if ./configure script finds everything he needs. I mean all the good things what developers are meant to be used when they present. I think this is the other way of tuning up system speed besides optimization.

I hope you understand what I mean.

If configure finds everything it needs, it will build all of the possible options into the program. For example, a program may have two versions - a GUI and a command line, but the GUI may use GTK. Configure could check to see if GTK is present and only build the GUI if it is. Or a program could have support for writing sound to both OGG and MP3 formats. Then configure would check that libogg and lame were installed, if not it would not build the appropriate support. If you want things to be faster, you can build them statically, although this has several disadvantages (see LFS book)

I got a picture. Thanks. So there is no such thing as doing thing other way if the best way is not obtainable.

But there is still a but. I'm confused. When I compile LFS, then with some packages I see they are sayin that fortran compiler and his things were not found. Do I have to accept whith the knowledge that fortran support will not be compiled.

I'm just inquisitive. I wanna know everything, but that is obviously nearly impossible.

Not quite. Some programs might for example, be optimised to use one thing, but be able to use an alternative and will check for both, use the best if possible, but otherwise use the other one.
As for the FORTRAN thing, I'm not sure - very few programs would want to use this. I've been wondering about this myself, but I don't think it's anything to worry about