While their basis for this was not chemical reasoning but observed results, the reasons fundamentally were that an enzyme in the body (aromatase) converts a portion of testosterone into estradiol, which is an estrogen. Abnormally elevated estradiol can cause gynecomastia, acne, and water retention, all of which they wished to avoid.
At doses such as the above, estradiol typically remains in the normal range and only in particularly sensitive individuals is there any noticeable adverse effect.
Without an antiaromatase drug, as testosterone dosage increases beyond that, estradiol levels tend to increase outside the normal range. In terms of being bothered by effects other than sometimes facial or back acne, many have no substantial estrogen problems at doses of even two or three times the above. In terms of measured estradiol levels, however, higher doses do ordinarily cause abnormal elevation.
Since there were no anti-aromatase drugs available back in the day, aromatization was an excellent reason to limit testosterone use.
Today, anti-aromatase drugs such as Femara Letrozole are readily available. If using an anti-aromatase, then testosterone dosage doesn’t need to be limited for this reason.
In terms of general physique look, other than effect on estrogen I don’t find there’s any difference between the different oral anabolic steroid or between different dosage levels. The only questions are anabolic effectiveness, side effects, cost, availability, personal preference, and genetics. Not genetics regarding what anabolic steroids will work for the individual, but genetics for the sort of physique that will result from training, nutrition, and drug use.
As you’re looking for substantial but not necessarily maximum possible results and you sound more health-oriented than extreme-results oriented, there’s no need to get complex. I’d use at this point a minimum of 500 mg/week total and up to 750 mg/week. Not that more than this cannot be used, but it sounds as if you do not need it. This could be with testosterone as the only anabolic steroid, preferably combined with an antiaromatase such as letrozole. Preferably, estradiol level would be measured by blood test after 2 weeks, and the antiaromatase dose adjusted if needed.
Another choice would be to use testosterone at only 200-250 mg/week, and make up the balance with Masteron, Methenolone Acetate Primobolan Pills, or trenbolone.
Still another choice would be use Masteron Dromostanolone Propionate or Primobolan at 500-700 mg/week, or trenbolone acetate at 50-75 mg/day, and add HCG at 700-1500 IU per week. HCG is another way of providing testosterone, by stimulating your testes to produce it.