Advanced Sharpening Question

[ender18d]

Here's a question for some knowledgeable types here:

I'm trying to improve my sharpening and getting decent results but trying to get better. I have the Edge Pro Apex with their complete line of stones and tapes (the "4" kit, up to 1000 grit water stones). I also have a balsa strop with green compound. I am currently trying to sharpen 3 steels:

Al Mar Mini Sere in VG10
Benchmade Osborne in S30V
Spyderco Para2 in S35VN (sprint run)
(Plus some Shun kitchen knives)

I have not yet sharpened the 3rd as the factory edge is still pretty good.

I did reprofile the Osborne with the stock stones to 21deg and its shaving sharp, but not as sharp as some knives I've seen with the same steel.

I have been reading that for the S30/35 may require/benefit from diamond stones. Is this a need or should I just keep working with the stock apex stones... or would I alternately be able to use something like a Shapton Glass? What would be your recs? Understanding that as I go down the rabbit hole I might wind up playing with some of the more exotic steels later on as well.