Many PS' and PH's are not non-aromatizing. Epi and some milder ones are, some like SDrol are pretty rough. SERMS are used to bring down the levels of E. If your body is getting super low natural T, but a spike from outside T, your estrogen levels will react to the outside T and not stay low to counteract the natural low T. It's when you stop the cycle that your natural T is low and your E level is high that you get aromitzing side effects. Which is why people need thier SERM and a test booster to bring the body back to homeostasis. A SERM is not a natural test booster, but a selective estrogen reducer this giving your body the ability to raise natural T to proper levels. And you are totally correct you would not need PCT from test boosters. But before running anything real I would say doing some reseach on the realm of real supplements is def a must have.
Well, I'm not trying to play mr. correct or anything...you make great points about the research, being careful, and knowing the game you are playing...
However, I think there are alot of misconceptions on SERMS, estrogen, and steroids in general.
SERMs are Selective Estrogen Receptor Modulator...they are not "Anti-Estrogens" I've actually read about them a pharmacology text book that refefres to SERMs as "anti-estrogens". I may be wrong on all of this, but SERMS actually BLOCK estrogen from selective receptors...like the breast tissue, and somehow show some sort of imbalance of estrogen to the pituitary which causes the pituitary to drive up LH, thus increasing test levels substantially if they leydig cells are fully responsive.
Clomid (clomiphene citrate) actually is made up of an estrogen, and a SERM like estrogen. Clomid will actually exhibit estrogenic sides besides breast tissue enlargement. People experience mood swings, depression, anxiety, all of the classic high E symptoms on clomid, because its actually an estrogen that binds to the receptors BEFORE the bodies natural.
On the other hand, Aromatase Inhibitors (such as Arimidex, letrozole, formestane, etc) - these bad boys actually eliminate estrogen. They either block or completely eliminate (suicidal) the aromastase enzyme.
Now during a cycle, especially a non-aromatizing, the "outside" T, exogeneous, or whatever you want to call it isn't going to affect the estrogen levels in the body...its not going to aromatize. Its impossible for havoc, superdrol, pheraplex, halodrol, winstrol, trenbolone, M1T, and so forth to cause raised estrogen levels IF they are truly meant to be non-aromatizing. The fact is, some of these compounds will accidentally aromatise in ways we can't understand because the lack of medical research. In such a situation, you are correct, the outside T may be recognized and aromatized causing estrogenic side effects. To counteract this issue, an Aromatase Inhibitor is utilized, not a SERM. A SERM will only work in blocking gyno, wheres the AI will actually solve the root of the problem.
Any other problems experienced on cycle such as low-libido, lethargy, mood swings, "roid-rage", headaches, insomnia, brain-fog...are caused from the LACK OF natural testosterone that results from using a steroid without testosterone base.
After a cycle, SERMS are used primarily to jumpstart the brain into producing LH. Their primary goal is not to block estrogen after a cycle. Estrogen should be extremely low in textbook case after a non-aromatizing cycle. Think about it...the cycle kills your natural T though the inhibition of LH, without natural T you cannot make any E, the steroid isn't aromatizing so you aren't recieving any E, and now you stopped the cycle...so you have ZERO hormones.
The SERM is most powerful test booster of all time. Clomid hits your pituitary hard and forces high levels of LH. Testosterone flood your system from 0-lets say 700ng/dl...on top of this, you E levels have been suppressed and the non-aromatizing hormone can cause your aromatase enzyme to fight back and overproduce causing that T to convert massively to E....the SERM will block the breast tissue to even things out and then an AI can be administered to slowly bring the aromatase enzyme back down to stable levels as you discontinue the SERM.
Just trying to help you clear some things up. So in regard to a test booster, theres no supression of estrogen, unless you are using an AI based test booster...where in that case it just drops E and raises the ratio of T. Then all you need to do is taper down. Natural test booster are NOT "outside" T as well, so they won't cause estrogenic problems.