Honestly, it's ALL speculation. There are no GREAT studies either way, long-term at least.
Some can use gear their whole life and be fine (I think I saw someone on here who stated they used 500-1000mg test/week for 20 years and never had a single issue). Some can do it once or twice and wreck themselves even WITH proper protocols. and then there are the latent issues that we just don't know about, and can't ever "prove" if they were even caused be AAS use.
Genetic response/tolerability of AAS is HUGE.
The study looking at 600mg/week was done for 20 weeks, and those people weren't followed long-term. From a short term POV, it looks like they had no real issues with 600mg/week for 20 weeks. Which is a good thing to at least see and have in the ol' database.
But even those saying "just do TRT and blast a few times per year" - well, there are no "studies" showing this to be the best. It's speculation, although it does seem to be intuitive.
But considering what I know of medicine (just a dumb MD here), I know that few things are rarely intuitive, which is why good double blind placebo-controlled RCT's are needed.
I would say it's going to come down to the individual (I know, I already said that).
I DO think cycling is worse for a person's health. PCT is, in my opinion, insane. If you're going to commit to many cycles, then I think one needs to commit to TRT. If only a couple cycles, then yeah I can maybe see PCT being fine, or just doing nothing and letting things kick back in on their own.
But again, this is speculation, even.
Just accept the risks YOU are willing to accept.
I have accepted there is are risks of even being on TRT, but there are studies that are fairly convincing showing even worse outcomes for long term low T.
I have also accepted the risks of blasting for prob more than half the year. I get bloods every 6-8 weeks. And even then bloods prob don't tell the whole story, but it's what we have.
Life is short. You risk dying every day. Minimize risk the best you can in your own situation, based on your goals. I think that's the best you can do.