1+1 = 3 is more accurate. Stacking is best, its why we do it.
After a certain point more test really just gets you more strength, but it does that very well.
Pretty much always until you hit 2-4 grams a week. You can just keep upping the test and it keeps working just fine.
Yes you hit noticeable diminishing returns after about a gram a week, some people mention 750mg, I say 1000mg, pretty close.
But putting more test on top always works, throw another gram, you get stronger, another gram, stronger.
"Test is best" is a common saying for a reason, its cheap, its a hormone that your body is comfortable with, with estrogen controlled it has almost no side effects, it does everything very well, and it does not suffer diminishing returns nearly as fast as other drugs.
But jacks of all trades tend to be a master of none. If your looking to prioritize adding tissue, you need to add a compound that is a more dedicated anabolic, deca, tren, EQ.
Hence stacking, but a smart user does not cycle without test unless they have to, its cheap, its effective, its hassle free.