Configuration of current kernel

[h p]

Hi,
I'd like to recompile my kernel for disk encryption support (options
GEOM_BDE). I am right now running an out-of-the-box 5.3-RELEASE
kernel.
I noticed that some kernel modules I use are missing in the GENERIC
kernel configuration file (such as ext2fs and snd_emu10k1). I am
worrying that these features will not work if I install a new kernel.
Of course, I could just try and restore the old kernel, if not.
With Linux, there is a solution to get the current kernel
configuration (in /proc/config.gz). Is there such a thing under
FreeBSD?
I admit I haven't yet quite understood how the kernel recompilation
works. How do I configure features as a module? Also, there are some
features, which don't seem to be documented... at least not in the
NOTES file. ext2fs is an example. Is there a comprehensive list
anywhere?
Thanks
Helge