Good questions man. I would say E2 is literally night and day difference. My first cycle which i ran with my best friend, i was like every other guy at first, had no idea how to manage E2 or how i would aromatize. So i went till week 5 until i got blood work and it showed my E2 being 5X the normal range, i swear to god. Started taking 12.5mg aromasin by feel, mostly once a week, sometimes once every 2 weeks, and my e2 was still very high, despite that i felt great apart from having a little softer erections and hit and miss libido. Muscle building wise it was amazing, i looked full as fuck and was getting huge, put on 20 lbs solid that cycle and remained 10% bf. I know it's hard to believe but i can post a picture for proof.
Next cycle comes and i do 500/500 test/eq, i look good, veiny, lean, dick works fine, but my libido is non-existent and i get annoyed easier. Take bloodwork mid-cycle and see that my E2 is crashed. It's at 6. Shit... i wasted all this time for negligible gains. I instantly drop the eq down to 250mg but it has a crazy half-life, so i don't get to experience that same muscle-building as i did at first. It went back to low/mid-range but never got up to high again. Also, i didn't feel nearly as good mentally as i did on high E2. I think it's a lot about balancing the E2:TT ratio. I also learned this time around that E2 is very cardioprotective and anabolic. Low is VERY unhealthy.
EQ and Primo seem to be the holy grail for people like you who aromatize a lot. My best friend included. He felt shit the first cycle, developed gyno, and was bloated as fuck despite taking 12.5mg aromasin twice or three times a week. Second cycle which was the test/eq one he had an amazing time, made amazing gains, and didn't even need aromasin. So it's very interesting to think about.
As for not wanting to go above 600mg test, i don't see a reason for it, not to sound like a douche but i think i look better than 99% people on test alone, i have a hard work ethic, decent genetics and my diet is on point. So i don't see the need to go above 1g total gear. More gear equals more side effects, and i try to run a healthier approach than the majority. If i was competing i would see a reason to do it, but i don't. I am in it for the marathon, not the sprint.