My prefered ones are WestoneAudio AMpro30.
These are semi-opened ones : ambient noises and music are heard -12dB. I will not say they are perfect, but they help me much in playing, and most of all, singing right.
I also own some Shure 535, which are certainly much wider frequency range, but they don't help me singing right, and of course they are closed type.
BTW the AMpro30 are presently discontinued.
IMHO, extended bass frequency range and bass prominent devices are to be avoided when it comes to IEM.
You will always hear and feel low frequencies thru your head and chest from any high level PA. So some sort of little weakness in deep bass is a good thing for feeling right with IEM on stage. As usual YMMV.
Jus sayin', my buddy playing sax and bass clarinet is totally happy with his Shure 215.