Without any specific knowledge about this subject, the thing I would do in your case were og course reading
Did you do that?
You also need to be aware of thye fact that things that go anywhere in ~/ are only for that specific user. Things going in /etc/ are system wide for all users. Thus if what you want is typical an end-users wish, it never should be configured on a system wide base because another user may want different. This is true even if you think “there is only one real user of the system”, because the fact that on this system there is only one does not change the rules that Linux is a multu-user, multi-session operating system.
~/.xinitrc will be used instead of default session startup script, so you would need to add complete sequence to start your DE. So I would say either use your DE to autostart programs on login or create /etc/X11/xinit/xinitrc.d script to do it.