Test levels gradually build for 7 days, where they peak. If you continue to not be sexually active, they return to baseline lower than before.

a) It’s known that short-term abstinence of 3 weeks can slightly increases testosterone levels in healthy human subjects, and one interesting study shows a significant 145% spike in T at the 7th day of abstinence (probably an evolutionary trigger to reproduce). However, long-term abstinence of 3 months has been shown to significantly reduce testosterone levels.

Short-term abstinence from ejaculations can slightly increase testosterone levels.
Long-term abstinence can reduce serum T.

Having an ejaculation does not acutely affect testosterone levels.

Ejaculating to the point of “sexual exhaustion” can make it harder for your body to utilize testosterone.

Masturbation doesn’t seem to affect testosterone levels in any significant manner.
Sex with a real person can boost testosterone levels significantly.

So to answer the question is it better for test to regularly masturbate or not, the answer is to do it. Also there isn't a linear relationship between testosterone and androgenic effects... and the normal range is 400-1100.

There won't be any real difference until you get to superphysiological amounts.