Combination simply for the sake of combination doesn’t improve results. In contrast, some specific combinations do help, where compounds work synergistically with each other.
These bases are already covered when having the oral anabolic steroids you first mention. Any additional oral anabolic steroid may be used, but when they are used, there’s not a point to adding them to the above. Instead, they might be replacements.
But they would be replacements for no particular reason. I don’t find a special advantage to any of these compounds. An exception certainly can be where experiencing a personal result. If for example an athlete has experienced enhanced endurance performance from Halotestin Fluoxymesterone (most likely from effect on the CNS) then certainly it might be used again even though others may dislike it for water retention reasons. Likewise, if a lifter has found enhanced performance in the gym from methyltestosterone, high might continue to use it, although others might dislike it for its effect on liver values.
In the case of Halotestin, a likely reason for its particular adverse side effect profile is strong inhibition of an enzyme (11b-hydroxysteroid dehydrogenase 2) which acts to reduce the potency of cortisol. By increasing its effective activity, it could disturb electrolyte balance and cause water retention. Again, this doesn’t mean it can’t be used, but it’s a reason for it to not be in the first tier among oral anabolic steroids.
Oral Turinabol might be used where a person wishes to use only a single oral steroid and get reasonable mass and strength gains. Generally I don’t see a reason to limiting to only oral use, let alone only one oral compound, but some do want to do it. I’d certainly recommend, for example, a Dianabol Methandienone/Anadrol Oxymetholone stack instead, though if going oral-only, and even moreso I’d recommend a good injectable/oral stack.
In general, there seem more issues of water retention, adverse effect on blood lipid profiles, and worsened liver values with the latter steroids mentioned than the first group, but not to so great an extent as to rule them out. They simply are not my first choice, and nothing is lost by keeping choice within the first-mentioned orals.